[Klonoar]

There's a fork of this as well, though I don't know much about why the fork happened or anything:

http://kolibrios.org/en/

[snvzz]

License. MenuetOS is proprietary. KolibriOS is open source.

[sigzero]

I couldn't find anything about why. It's only the 32bit version it seems. 32bit MenuetOS is GPL but the 64bit is a different license.

[anta40]

I haven't touch KolibriOS for a few years. It used to be 32-bit only, not sure today.