Do they really? I can only think of a couple times that I've seen artists selling tabs themselves. If it's a music book, I've found them to be about as reliable as ultimate-guitar.com (which is to say, they're hit or miss)
But either way, this is awesome
I know Led Zepplin is blocked on UG over here in the UK (strange...) and so is Feeder iirc. So, yeah, you have to buy it rather than get it for free. I'm sure there are more too.