What you need
is an Eclipse Foundation like setup where large
corporations/system integrators make money on complementary services
and therefore can afford "altruistic" contributions to a real
open-source project like MediaWiki. Well, not only "afford" but
"have to". :-)
As much as I support open source concepts I have to admit that most of
it remains untested in the courts. Patents can be a bigger problem than
copyrights because they cover the ideas rather than just the expression
of the idea. The first person to the patent office has an advantage
even over others who may have had the idea earlier.
That's why you need a proper setup. The Eclipse Foundation, for
example, requires signing away any claims based on patents used in
source code contributions before they get accepted. It should be the
same for MediaWiki and related contributions.
Dirk