That's my personal perspective too, and why I don't use "non-commercial use only" licenses for my own projects. There's a good reason the GPL does not exclude commercial use, and it's not because the FSF are a bunch of raging capitalists. It's because defining "commercial use" is actually not all that easy (I've seen some lawyers suggest that using an NC-only asset on a free Wordpress blog might be a violation, because the presence of ads makes it commercial use), and such restrictions are unnecessary anyway provided the "sharealike" clauses are complied with. Indeed, it's actually quite common for commercial users of GPL code (IBM, Red Hat, even Microsoft these days) to contribute valuable improvements to that code, so locking all of these companies out of the ecosystem would not benefit anybody.
However, changing the license of the Dark Mod itself is pretty much impossible for reasons that others have explained.