Warning: This is alpha software.
Ok so Skoar 3 is a rewrite in C++. It's at least 1000 times faster than the supercollider version, and has many really cool language improvements. Everything is better about it. Except the part that makes music, it does work, there's a MIDI proof of concept, and then development fizzled out.
It is unusable on it's own, consider it more like a "libskoar". The license is now MIT.
The separate project Editoar is an IDE/debugger/testbed that can use it. I don't recommend using it to make music, it's simply not ready. However it is essential for working on the language. The license for that one, a requirement for using the JUCE C++ libraries, is that it is GPL'd with GNUv3.
Editoar: https://github.com/sofakid/Editoar
Sorry. It's not done, it's been years and I'll never finish it on my own.