>Mono implements an international standard albeit one from a convicted monopolist. If this is a problem, why do people use C, the standard from convicted monopolist AT&T? Mono implements an improved, Free replacement for a proprietary offering. If this is a problem, why do people use GNU (which provided an improved, Free replacement for proprietary UNIX)?
AT&T was barred by consent decree from entering the computer industry. Unix and C were, by the standards of the day, practically given away, and AT&T couldn't use the control over these they had to unfairly outcompete other companies.
Mono implements a _subset_ of a proprietary offering that is Free (as in speech and beer). GNU is pretty much a greatly enhanced superset of AT&T UNIX.
But I get your point. Since then, AT&T got a lot more civilized.
Microsoft never was.
I know many people that would question your claim that GNU 'enhanced' the work of Bell Labs, more like the opposite, but then they were certainly not alone in that.