That's a great example of a mod that just plainly repairs a deficiency in the original game! I was in fact struggling to think of one.
It's clear that this game is abandoned and there's no further support coming from Westwood Studios for it, not to mention that it won't be coming available on Steam any time soon. As troubled as this analogy is, ...
I think it's still clear that in a hypothetical scenario where Steam gets the rights to distribute RA2 and Westwood (EA? who owns the rights to C&C series now?) has still washed their hands of support for it long ago, it would make sense for Steam to give the mod authors the option of sending back some percent of the gross (1-10%) to the rights holders for the game. Sort of a "vote with your dollars" kind of thing.
Of course if we are really talking about sending "extra money" to EA to say thanks, as a mod author or gamer I'm probably going to need to vomit right away, but replace EA with some other hypothetical not-shitty company (the ghost of Westwood) and I think you've got a deal.
This whole scenario just makes me reflect on the relatively recent development of Apple deciding that they can't allow any apps in their phone store that mention support for any products competing with Apple Watch (misfit, fitbit, etc)
The way this played out just goes to show who really owns the greatest share of the attention of Valve and Steam (it's the game companies, not the mods or the community.)