From the README.md file:

> License terms

> The PicoVGA library source code and the PicoVGA library sample programs are freely available for further use and modifications. This does not apply to certain graphics and sounds (such as the sounds in Pac-Man) and scene definitions in Sokoban, as these are subject to third party copyrights and may be subject to different distribution terms.

Not a very well-defined one, at least.