I just want to clarify that there are two well-known software packages called
"Unity", and only one of them is libre.
The one that is libre is the desktop environment developed by Canonical and
used by default in Ubuntu -- though do note that it is a rare case of libre
malware by default (you need to turn off automatic sending of searches to
Canonical for it to not be spyware).
The other software package called "Unity", or alternatively "Unity3D", is a
game engine and IDE developed by Unity Technologies. This software package is
proprietary, plain and simple.
