Advice appreciated on community contributions approach

I suspect I'd settle for "you give me the right to exempt people from the requirement to provide source, provided the binaries are unmodified".

That way, I could licence commercial companies to sell a binary-only, "proprietary" product, but they would lose the right to make proprietary changes. If they wanted to change the source, they would have to give their changes to me for me to make them freely available, in order to be able to distribute their changes.

Cheers,
Wol