VPNs aren't explicitly blocked here, but a lot of them do get blocked by our spam filter. This board (like a lot of forums with adult content or even forums in general) gets hit pretty hard with bots posting spam and illegal content. We manage to kill most of it before it starts with a series of filters, both automatic and manual, but one of the downsides to this is that several VPNs that are commonly used also get caught in this net.