Originally I believed the author may be the sole author of Menuet32, and thus could relicense to whatever they wanted. However, the release notes (https://www.menuetos.net/relnotes.htm) credit many other authors with their contributions.
The project kept growing a bit, very slowly. Seems like after v1.00 the author lost most interest. So if it is still a prototype work without any commercial usage, it would be great to have it published with source code.