This is specifically mentioned in their FAQs for developers wanting to use the system. If your mod uses other mods as a backbone or in part, then it is your responsibility as the modder to come to an agreement with the original creator.

Valve has a known history for using TF2 and Dota 2 as their test subjects for new experiments. TF2 has a modding scene in the form of cosmetics and weapons that Valve has supported and tampered with for years, and hundreds of modders have been paid by Valve to use the assets they created. Nobody raises hell about that, nothing about stifling creativity. For TF2 and Dota 2 they seem to be really good systems.

People want to blame Valve solely on this, but Valve is only as bad as the people that want to abuse the paid mods system. If you have a modder that is going to steal from other modders or give a faulty product, that's not Valve's problem -- the modder is the person at fault.

People want to complain about the monetary splits, fine, but Valve itself has a set rate. The game dev sets the rest of the figures on how much they want and how much the modder gets. Get mad at Bethesda for only letting the modder get a 25% cut. From my understanding of it, a company that truly believes the modder deserve's the lion's share could allow them to get 70% of the total take, and that's a pretty fair slice.

But what we don't need are a bunch of armchair sales analysts that apparently know the market better than the game devs and industry tycoons that somehow take advantage of modders that submit to this system on a non-compulsory basis.

People stealing mods and hosting them on Steam? Flag and report them. Best-case scenario Valve will actually use their 30% cut to invest in this system so that they can verify content creators and take action against those stealing.

The project's been out for a little over a day and this shitshow is embarrassing.