As long as people are rational about this sort of thing and don't pay money for [censored] mods, this should turn out alright (though changes will occur as always happens when money is introduced).
If a new modder appear and starts charging for every mod they make? Ignore them. They will either go to free mods or leave. Money-grabbers jumping on the bandwagon are not the sort of modders that this community needs.
If a known modder comes out and says 'x new mod I'm working on is going to be paid' then instead of howling them down about the money, just consider if the 50c or whatever that they ask for is reasonable for the amount of content in the mod. If it's not don't buy it, again either the mod will fade away into obscurity, or it will go to free.
The last thing we want is anger and hatred dividing up the community and driving good modders away. Deaththreats aren't going to make a mod free, it'll just make the creator leave, and the last thing such a long running and friendly community needs is people leaving.
I would never have charged for any mod that I made in the past (nor would even asked for donations) as I worked with others and learnt from things they did to make my mods, along with my own experiments. My modding was done as a hobby and to learn how game systems worked, the whole reason I left modding was to purse actual game development instead. But I can see very large mods like DLC size quest chains, or world overhauls that could and should work with this paid model.
But any modder looking to make paid mods has rocks in their head if they think 25% is anywhere near enough for the work that is put in. On that figure alone modders should boycott this program. And if mod users want to support their favorite modders, look to give donations which a much larger percentage actually goes to the modder. As soon as modding is made into an 'industry' we need to be able to discuss reasonable terms with the publishers the same as a union would do in other industries, unfortunately we obviously don't have a union and are having the terms dictated to us.