I was looking at this answer, and noticed that it required that the GNU Pascal compiler to not be installed on the system. Is this allowed?
As long as there is some configuration of hardware+software available that can be used to reproduce the results from the submission, anything goes, even requiring certain software to be installed and certain other software to not be installed. This is parallel to our rule on compiler-specific submissions.
I don't think we need a ruling on this. It has only come up once, for a popularity contest that asks for the "most creative" answer. Feel free to vote on that answer based on how legitimate you find it.