Sure, and that alone isn't an unreasonable premise - as he says, intent matters. But if you're marking interfaces as GPL-only, or implementing taint detection

Sure, and that alone isn't an unreasonable premise - as he says, intent matters. But if you're marking interfaces as GPL-only, or implementing taint detection that means if you use a non-SYMBOL_GPL kernel symbol which calls a GPL-only function it treats the non-SYMBOL_GPL symbol as GPL-only and blocks your linking, it gets a bit out of hand. Building the kernel with certain kernel options makes modules like OpenZFS or OpenAFS not link because of that taint propagation - because things like the lockdep checker turn uninfringing calls into infringing ones. Or a little while ago, there was a change which broke building on PPC because a change made a non-SYMBOL_GPL call on POWER into a SYMBOL_GPL one indirectly, and when the original author was contacted, he sent a patch reverting the changed symbol, and GregKH refused to pull it into stable, suggesting distros could carry it if they wanted to. (Of course, he had happily merged a change into -stable earlier that just implemented more aggressive GPL tainting and thereby broke things like the aforementioned...)