i know a lot of smaller companies that don't care. they see it as the modders taking the time out of their lives to work on content for the game.
the larger ones see it as profit they are not getting.
What IGS stance is, idk.

me, i make mods as well. and in fact people can pay me for them. as i have donation links. but i don't lock content behind a paywall. though that is a interesting idea. as i never seen how to do that. but in a way its a neat idea as well. some mods take year's to make and are quite extensive. i seen some that make it into the base game as well.