:) It was more just for the point of clarity. I understand you are trying to
alleviate other peoples concerns too. We could have replaced non-free with
"other licensed". Other licensed software could be a free software licensed
program under a different license than the GNU GPL.
We are talking about license compatibility. The clearest example is with free
and non-free software.
This issue is pretty common and there are people out there who would mislead.
These tend to be non-free software proponents.