Couldn't care less about the porn, personally, I mean, there's a million places on the internet to see porn, never really got the draw of the porn to the forums but whatever.
Was willing to drop 10 bucks to read SA forums when they're closed to non members (after years of lurking), would be willing to do the same here if needed. Don't mind ads, or the screenshots thread going behind a posting wall, I figure if that's the worst that happens, that's a pretty good deal, really. I mean they could be putting up a paywall for membership and trying to turn this into a Something Awful clone, and they're not, and nothing in life is free, so yeah.
Sounds like something you feel you need to do to trim costs and keep the forums running, that also sounds perfectly reasonable, so no complaints here.