The launcher
The Phaethon launcher is proprietary software. The license it shows during setup governs its use.
The runtime
The runtime, the compiler and the decompiler come under two licenses, by who wrote what. Phaethon's own work, everything added since the fork left OpenGOAL's jak-project, is under the PolyForm Strict License 1.0.0. The code inherited from OpenGOAL stays under the ISC License with the OpenGOAL Team's copyright notice. The License page says what each allows and carries both texts. Both give the software as it is, without a warranty.
The runtime builds on the OpenGOAL project's work, and Phaethon thanks everyone who contributed to it.
The games
You need your own copy of each game you play. Phaethon ships no game data and downloads none: the launcher reads every file from your own disc or an image you made from it. Phaethon is an unofficial fan project, not affiliated with, endorsed by or associated with Sony Interactive Entertainment, Naughty Dog or the OpenGOAL project. Jak and Daxter is a trademark of Sony Interactive Entertainment.
Questions
Write to hello@playphaethon.com.