Compatibility Guide

This document outlines how the Public Prompt License (PPL) family interacts with other common open source licenses.

Summary Table

License	Compatible with PPL-M?	Compatible with PPL-A?	Compatible with PPL-S?
MIT	✅ Yes	✅ Yes	✅ Yes (One-way)
Apache 2.0	✅ Yes	✅ Yes	✅ Yes (One-way)
GPL v3	✅ Yes	✅ Yes	⚠️ Complex
AGPL v3	✅ Yes	✅ Yes	⚠️ Complex
Proprietary	✅ Yes	❌ No (Attribution req)	❌ No

Inbound: You can include MIT, Apache, or BSD licensed text into a PPL-M project.
Outbound: You can include PPL-M prompts into any project (GPL, Proprietary, etc.), provided you retain the license file.

Inbound: You can include MIT or Apache licensed text.
Outbound: You can include PPL-A prompts into GPL v3 projects (Apache 2.0 is compatible with GPL v3). You cannot include them in GPL v2 projects.
Patent Note: The patent grant in PPL-A is identical to Apache 2.0. This provides strong protection for downstream users.

The "Viral" Effect: PPL-S is a "strong copyleft" license for prompts.
Combining with Code:
- If you have a project with AGPL Code + PPL-S Prompts, the result is effectively a "Double AGPL" system. You must share the code (under AGPL) and the prompts (under PPL-S). This is a highly compatible and robust combination for open-source AI services.
- If you have Proprietary Code + PPL-S Prompts, you must be careful. You can keep your code closed, but you must share the prompts if you run the service. The PPL-S "Scope Limitation" protects your code from being infected, but you must strictly separate the two.

We are in the process of submitting PPL to the SPDX registry. Until then, use the following identifiers in your LICENSE headers: