They've already effectively prohibited it because, as you can see from the article, installing software that doesn't go through Apple is made incredibly painful and essentially nobody will succeed in doing it.
Apple doesn't really care that you can run it by using a bunch of workarounds if they have 99.9% control over all software distribution.
Apple doesn't really care that you can run it by using a bunch of workarounds if they have 99.9% control over all software distribution.