Do you have *any* reason for this? Mono has no code from MS. The license (X11) is the same license your XFree86 server is under, so don't try to say you refuse to run X11-licensed code. Besides, there are many perl-GTK apps, and Perl is not GPL.
I'm imagining the only reason you are saying this is because Mono is based on a small portion of what Microsoft calls .NET, and you don't want to run anything designed by Microsoft.
Mono is only based on the standardized parts of .NET. Mono runs no MS code. Mono cannot be controlled by Microsoft - if Microsoft tries anything funny, Mono will simply cease being compatible with Microsoft, which would basically mean the same thing as if we created our own technology anyways.
And in any event, if you are avoiding everything Microsoft, you had better get rid of all your CD drives (Microsoft holds a patent on some part of the firmware in all CD drives, as I read anyways).
Please, tho, before you start spreading FUD and hate for GNOME, try understanding what you're talking about first. There is plenty of documentation describing Mono, licensing, Microsoft compatibility/interoperability, and every other question you might have, at http://go-mono.com, if you would actually bother to read it.