"It therefore surprised some when Canonical, the company behind
the Ubuntu Linux distribution and an ardent opponent of software
patents, decided to include Mono in its standard distribution. The
company publicly defended its decision and, in my opinion, was
right to do so. It's simply a matter of pragmatism, as John Mark
Walker points out because "if we ditched all free software for
possible patent violations, we'd have nothing left."
"Now Microsoft has ostensibly made everything easier for Ubuntu
and the rest of the Mono-using world, by pledging not to assert its
patents against Mono developers, distributors, and users (i.e.,
those that implement C# and CLI, ECMA specifications 334 and 335,
as Mono does)."