Again, you are like 40 years late, or maybe 50:
- Whole Unix clones, kernel and userland
- Unix userland utility clones
- Unix compiler and linker packs. Tons of them.
- Unix UI clones 99% close to the original API
By 2000/2001 you could run most GL accelerated stuff under MESA+DRI just fine as if it were an SGI machine, even replacing propietary Motif with LessTif.
- Windows API clones, both for running and compiling software, with WineLib+WineGCC or MinGW.
- Windows clones, ReactOS from GIT can be fairly complete.
- NextStep/Cocoa clones. Currently tons of software made for OSX 10.6 (in a libre way) can be compiled with both GNUStep+Addons and with XCode.
- Whole Unix clones, kernel and userland
- Unix userland utility clones
- Unix compiler and linker packs. Tons of them.
- Unix UI clones 99% close to the original API
By 2000/2001 you could run most GL accelerated stuff under MESA+DRI just fine as if it were an SGI machine, even replacing propietary Motif with LessTif.
- Windows API clones, both for running and compiling software, with WineLib+WineGCC or MinGW.
- Windows clones, ReactOS from GIT can be fairly complete.
- NextStep/Cocoa clones. Currently tons of software made for OSX 10.6 (in a libre way) can be compiled with both GNUStep+Addons and with XCode.