"Yes, Mono is based on Microsoft's .NET. Like it or
not, several valuable open-source programs like Tomboy, a
well-regarded note-taking program; Moonlight/Moonshine, which
enables you to listen and view Windows Media-bound music and videos
on Linux; and Banshee, my personal pick for the best Linux music
player, are Mono applications.
"Would it be better if these applications were written in some
more free software ideologically pure language? I doubt it. They
were written in Mono, not Python or C++. It's a pointless question.
If you don't like them, write better ones in another language. It's
the open-source way after all."