Proso Terms of Service

1. Introduction & Acceptance

These Terms of Service (“Terms”) govern your access to and use of Proso. “Proso” refers collectively to the Proso browser extension, the Proso managed text-to-speech server and API, the Proso website, and any related services.

By installing the Proso extension, using the Proso API, creating an account, or purchasing a subscription, you agree to be bound by these Terms. If you do not agree, do not install or use Proso.

Age Requirement

You must be at least 16 years of age to use Proso. This threshold applies globally to comply with the European Union’s General Data Protection Regulation (GDPR) default for digital services consent. If you are under 16, you may not use Proso.

Relationship to Open-Source License

The Proso browser extension source code is released under the GNU Affero General Public License version 3.0 or later (AGPL-3.0-or-later). These Terms apply to your use of Proso as a service. Where these Terms conflict with the AGPL-3.0 license regarding the extension source code, the AGPL-3.0 license prevails. See Section 13: Open Source for details.

2. Definitions

The following terms have specific meanings when used in these Terms:

“Extension”

The Proso browser extension, a software add-on for web browsers that provides text-to-speech functionality on web pages.

“Service”

The Proso managed text-to-speech server and API, which provides server-side TTS processing using managed credits.

“Account”

A registered Proso user account, required for paid features and subscription management.

“Subscription”

A paid recurring plan (monthly or annual) that provides access to managed TTS credits and premium features.

“Credits”

Managed TTS character credits allocated to your account based on your subscription tier. Credits are consumed when text is processed through the Proso managed server.

“BYOK” (Bring Your Own Key)

A feature that allows you to connect your own API keys from third-party TTS providers, enabling premium voice synthesis without using managed credits.

“Free Tier”

The always-free usage tier that provides unlimited browser-native TTS, word-level highlighting, and BYOK support without requiring account creation.

“Content”

Any text content you process through Proso for text-to-speech conversion, including web page text, selected text, and other textual input.

“Provider”

A third-party text-to-speech service integrated with Proso, such as OpenAI, ElevenLabs, Groq, Cartesia, or Google Cloud Text-to-Speech.

“Paddle”

Paddle.com Market Limited, our payment processor and Merchant of Record, which handles all payment processing, tax compliance, and invoicing for Proso subscriptions.

3. The Service

Proso is a browser extension that converts web page text into spoken audio using text-to-speech technology. It offers multiple modes of operation:

• Browser TTS: Uses your browser’s built-in speech synthesis engine. Browser TTS is always unlimited and free on all tiers.
• Managed TTS: Uses Proso’s server to process text through premium TTS providers. Managed TTS consumes credits from your subscription.
• BYOK: Uses your own API keys from third-party TTS providers. BYOK is always available on all tiers, always free, and your API keys never leave your browser.

Core Guarantees

• The Free Tier is always available without creating an account or providing payment information.
• Browser-native text-to-speech is always unlimited and incurs no charges.
• BYOK (Bring Your Own Key) is available on all subscription tiers at no additional cost.
• Word-level synchronization and highlighting is a free feature available on all tiers.

Service Modifications

Proso may modify, suspend, or discontinue any part of the service with reasonable notice. Where changes materially affect paid subscribers, Proso will provide at least 30 days notice and offer the option to cancel without penalty.

4. Accounts & Registration

Free Tier

The Free Tier does not require account creation. You may use browser TTS, BYOK, word-level highlighting, and all free features without providing any personal information.

Paid Features

Access to managed TTS credits, MP3 export, cloud sync, and other premium features requires creating a Proso account. When creating an account, you agree to:

• Provide accurate and complete information
• Keep your login credentials secure
• Notify Proso promptly of any unauthorized access to your account
• Accept responsibility for all activity under your account

Account Termination

Proso may suspend or terminate your account if you violate these Terms. You may delete your account at any time by contacting support. Upon account deletion:

• Your subscription will be cancelled (subject to the refund policy in Section 8)
• Your managed credit balance will be forfeited
• Proso will delete your account data within 30 days
• Your BYOK API keys, stored locally in your browser, are unaffected

5. Subscription Plans & Pricing

Proso offers the following subscription tiers:

Price Changes

Proso may change subscription prices with at least 30 days written notice. Price changes do not affect your current billing period. Annual subscriptions lock in the price at the time of purchase for the full 12-month term.

6. Billing & Payment

Merchant of Record

Our order process is conducted by our online reseller Paddle.com. Paddle.com is the Merchant of Record for all our orders. Paddle provides all customer service inquiries and handles returns.

By purchasing a Proso subscription, you agree to Paddle’s Checkout Buyer Terms in addition to these Terms. Paddle handles all payment processing, tax calculation, invoicing, and regulatory compliance. Proso does not directly collect or store your payment card information.

Billing Cycle

Subscriptions are billed either monthly or annually, depending on the plan selected. All subscriptions auto-renew at the end of each billing period unless cancelled before the renewal date.

Failed Payments

If a payment fails, Proso provides a 7-day grace period during which your subscription remains active. If payment is not resolved within the grace period, your account will be downgraded to the Free Tier. You will retain access to browser TTS and BYOK features.

Currency

All prices are listed in United States Dollars (USD). Paddle may display prices in your local currency at checkout for convenience, but billing is processed in USD.

Taxes

Paddle, as Merchant of Record, is responsible for calculating and collecting applicable sales tax, VAT, and other transaction taxes based on your location.

Cancellation

You may cancel your subscription at any time through your account settings or by contacting Paddle support. Upon cancellation, your subscription remains active until the end of the current billing period. After the billing period ends, your account reverts to the Free Tier.

7. Credit Policy

Credit Allocation

Managed TTS credits are allocated monthly based on your subscription tier (see Section 5 for credit amounts per tier). Credits represent the number of characters that can be processed through Proso’s managed TTS server.

No Mid-Cycle Expiration

Credits never expire during an active billing cycle. Your full monthly allocation remains available until the billing cycle ends or renews.

Rollover

• Pro, Multilingual, and Team tiers: Up to 100,000 unused characters roll over to the next billing period.
• Free and Basic tiers: Credits do not roll over. Unused credits are forfeited at the end of each billing cycle.
• Rolled-over credits exceeding the 100,000-character cap are forfeited.

Cache Efficiency

Proso caches previously generated audio. Listening to cached content does not consume additional credits — you are never charged twice for the same content.

Credit Exhaustion

When your managed credits are exhausted, Proso automatically falls back to your browser’s built-in TTS engine (always unlimited and free) or to BYOK if you have API keys configured. You are never locked out of text-to-speech functionality.

Transferability

Credits are non-transferable between individual accounts. Team tier subscribers share a pooled credit allocation among team members.

8. Refund Policy

Annual Plans

Annual subscriptions are eligible for a full refund within 7 days of the initial purchase or renewal, no questions asked.

Monthly Plans

Monthly subscriptions are eligible for a prorated refund for the unused portion of the current billing period.

Requesting a Refund

To request a refund, contact Proso support at support@proso.com.br or submit a refund request through Paddle. Refunds are processed by Paddle and typically appear within 5–10 business days.

Chargebacks

Proso reserves the right to suspend accounts associated with chargeback disputes pending resolution. If you have a billing concern, please contact support before initiating a chargeback with your bank.

Free Tier

The Free Tier is free of charge. There is nothing to refund.

9. API Keys & BYOK

BYOK (Bring Your Own Key) lets you connect your own API keys from third-party TTS providers to access premium voice synthesis directly, without using Proso managed credits.

Availability

BYOK is available on all subscription tiers, including the Free Tier, at no additional cost. You do not need an account to use BYOK.

Local Storage

Your API keys are stored exclusively in your browser’s local storage (browser.storage.local). Proso never transmits your API keys to Proso servers. API key data flows only between your browser and the third-party provider you have selected.

Your Responsibilities

When using BYOK, you are responsible for:

• Keeping your API keys secure and confidential
• Any charges incurred from your third-party provider
• Compliance with your provider’s terms of service and usage policies

Liability

Proso is not liable for charges, service interruptions, or data processing that occurs between your browser and your third-party provider when using BYOK. If a BYOK provider is unavailable, Proso falls back to browser-native TTS.

10. Third-Party TTS Providers

Proso integrates with the following third-party text-to-speech providers. When you use a provider (either through managed credits or BYOK), you are also bound by that provider’s terms of service:

OpenAI: AI-Voice Disclosure Requirement

OpenAI requires that AI-generated voices be disclosed to end listeners. Proso includes this disclosure within the extension interface. If you redistribute or publish audio generated using OpenAI voices, you are responsible for maintaining this disclosure to your audience.

ElevenLabs: Commercial Use Restriction

ElevenLabs restricts free-plan usage to non-commercial purposes only. If you use a free ElevenLabs API key through BYOK, you must not use the generated audio for commercial purposes. Commercial use requires a paid ElevenLabs plan.

Cartesia: Commercial Use Restriction

Cartesia restricts free-tier usage to non-commercial purposes only. If you use a free Cartesia API key through BYOK, you must not use the generated audio for commercial purposes. Commercial use requires a paid Cartesia plan.

Provider Availability

Proso is not responsible for the availability, pricing changes, service quality, or terms modifications of any third-party provider. If a provider becomes unavailable, Proso will fall back to browser-native TTS or another configured provider.

11. Acceptable Use

You agree not to use Proso to:

1. Process content you do not have the legal right to access or reproduce
2. Redistribute generated audio in ways that violate the applicable TTS provider’s terms of service
3. Circumvent or attempt to circumvent credit limits, rate limits, or feature restrictions
4. Engage in spam, harassment, or any illegal activity
5. Reverse-engineer, decompile, or disassemble Proso’s managed TTS server (the browser extension source code is open under AGPL-3.0 and is not subject to this restriction)
6. Share, resell, or transfer subscription access or managed credits to third parties
7. Use automated scripts, bots, or other tools to abuse the service beyond normal usage patterns
8. Use AI-generated voices to impersonate real individuals without their explicit consent

Proso reserves the right to suspend or terminate accounts that violate these acceptable use policies.

12. Intellectual Property

Extension Source Code

The Proso browser extension source code is licensed under the AGPL-3.0-or-later. You may use, view, modify, and redistribute the extension source code in accordance with the AGPL-3.0 license terms.

Proprietary Components

The Proso managed TTS server, API, branding, trademarks, and service infrastructure are proprietary. These components are not covered by the AGPL-3.0 license and may not be copied, modified, or redistributed without a separate license.

Your Content

You retain all rights to the text content you process through Proso. Proso does not claim ownership of your content.

Generated Audio

Ownership and usage rights for generated audio are determined by the terms of the TTS provider that produced the audio. Different providers have different policies regarding ownership and commercial use of generated content. Review your provider’s terms for specifics.

Commercial Licensing

Businesses requiring terms beyond the AGPL-3.0 license (proprietary integration, SaaS embedding, white-labeling) may obtain a commercial license. See COMMERCIAL.md or contact commercial@proso.com.br.

13. Open Source

AGPL-3.0 License

The Proso browser extension is open-source software released under the GNU Affero General Public License version 3.0 or later (AGPL-3.0-or-later). The full license text is available in the LICENSE file in the Proso repository.

Your Rights

Your rights under the AGPL-3.0 license are not limited or restricted by these Terms. The AGPL-3.0 license grants you the right to use, study, modify, and redistribute the extension source code.

Conflict Resolution

In the event of any conflict between these Terms and the AGPL-3.0 license with respect to the extension source code, the AGPL-3.0 license prevails.

Server-Side Code

The Proso managed TTS server and API are proprietary and are not covered by the AGPL-3.0 license. Server-side code is not open source.

Commercial Licensing

A commercial license is available for businesses that need terms beyond what the AGPL-3.0 provides. Contact commercial@proso.com.br for details.

14. Privacy

Proso is designed with privacy as a core principle. This section provides a summary; for complete details, see our Privacy Policy.

What Proso Collects

For users with paid subscriptions, Proso collects minimal data necessary for account management and credit tracking: your email address, subscription status, and credit usage metrics.

What Proso Does Not Collect

• Your browsing history or the URLs of pages you visit
• The text content of pages you read or convert to speech
• Your BYOK API keys (these are stored locally in your browser and never transmitted to Proso servers)
• Any data from Free Tier users who have not created an account

For complete information about data handling, third-party provider data flows, and your privacy rights, please review the full Privacy Policy.

15. Disclaimers

THE PROSO EXTENSION AND SERVICES ARE PROVIDED “AS IS” AND “AS AVAILABLE” WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT.

Proso does not warrant that:

• The service will meet your specific requirements
• The service will be uninterrupted, timely, secure, or error-free
• Results obtained from the service will be accurate or reliable
• The quality of any TTS audio will be free of errors, mispronunciations, or artifacts

AI-generated audio may contain errors, mispronunciations, unnatural pauses, or other artifacts inherent to text-to-speech technology. Proso does not guarantee the accuracy or naturalness of generated speech.

Proso does not guarantee any specific uptime or availability service-level agreement (SLA), except as may be separately agreed with Enterprise tier subscribers.

16. Limitation of Liability

TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW, PROSO’S TOTAL LIABILITY TO YOU FOR ALL CLAIMS ARISING OUT OF OR RELATED TO THESE TERMS OR YOUR USE OF THE SERVICE SHALL NOT EXCEED THE TOTAL AMOUNT PAID BY YOU TO PROSO DURING THE TWELVE (12) MONTHS IMMEDIATELY PRECEDING THE EVENT GIVING RISE TO THE CLAIM.

IN NO EVENT SHALL PROSO, ITS DEVELOPERS, CONTRIBUTORS, OR LICENSORS BE LIABLE FOR ANY:

• Indirect, incidental, special, consequential, or punitive damages
• Loss of profits, revenue, or anticipated savings
• Loss of data or business interruption
• Cost of substitute goods or services

ARISING OUT OF OR IN CONNECTION WITH YOUR USE OR INABILITY TO USE PROSO, EVEN IF PROSO HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

Some jurisdictions do not allow the exclusion or limitation of certain damages. In such jurisdictions, the limitations above apply to the maximum extent permitted by applicable law.

17. Indemnification

You agree to indemnify, defend, and hold harmless Proso and its developers, contributors, and licensors from and against any claims, liabilities, damages, losses, and expenses (including reasonable legal fees) arising out of or related to:

1. Your violation of these Terms
2. Your misuse of the service
3. Your violation of any third-party rights, including intellectual property rights or privacy rights
4. Content you process through Proso

18. Dispute Resolution

Governing Law

These Terms are governed by and construed in accordance with the laws of the Federative Republic of Brazil, without regard to conflict of law provisions.

Good-Faith Negotiation

Before initiating any formal dispute resolution, you agree to attempt to resolve disputes informally by contacting Proso at support@proso.com.br. Both parties agree to negotiate in good faith for at least 30 days before pursuing other remedies.

Arbitration

If a dispute cannot be resolved through negotiation, either party may submit the dispute to arbitration. However, in accordance with Brazil’s Consumer Defense Code (Código de Defesa do Consumidor — CDC), consumers are never required to submit to mandatory arbitration and may always choose to bring claims in their local court of competent jurisdiction.

Consumer Protections

If you are a consumer in the European Union or another jurisdiction with mandatory consumer protection laws, nothing in these Terms limits your rights under those laws. You may have the right to bring claims in your local jurisdiction regardless of the governing law specified above.

Severability

If any provision of these Terms is found to be unenforceable or invalid by a court of competent jurisdiction, that provision shall be limited or eliminated to the minimum extent necessary so that these Terms otherwise remain in full force and effect.

19. Changes to Terms

Notification

Proso may update these Terms from time to time. For material changes, Proso will provide at least 30 days notice through one or more of the following channels:

• Email notification to the address associated with your account
• A notification within the Proso extension
• A prominent notice on the Proso website

Acceptance

Your continued use of Proso after the notice period constitutes acceptance of the updated Terms. If you do not agree with the changes, you should discontinue use before the updated Terms take effect.

Impact on Paid Plans

If changes to these Terms materially affect paid subscribers, affected users may cancel their subscription without penalty within the notice period and receive a prorated refund for the unused portion of their current billing period.

Previous Versions

This is version 1.0 of the Proso Terms of Service. Previous versions will be listed here when updates are published.

20. Contact

For questions about these Terms or Proso services, please reach out through the appropriate channel:

• General support: support@proso.com.br or GitHub Issues
• Commercial licensing: commercial@proso.com.br
• Privacy inquiries: privacy@proso.com.br
• Security vulnerabilities: See SECURITY.md for responsible disclosure guidelines