NCsoft has a long and well documented history of aggressively going after private servers. The fact that Blizzard rolls in so much money from WoW that they don't give a shit is completely irrelevant.
There are currently 171 active Lineage 2 private servers, and that's just from one index site ( L2topzone ). And we're talking about their biggest title here. So, yes, they have shut down a private server here and there, but the cases of that I've found are similar to the ones that Blizzard has gone after: They got too big and well known and were making money off of them with paid memberships or some other means.
I'd think they'd have a harder time proving damages to warrant a full on legal action when it comes to a title that they've shut down and actively prevented access to through official means. But that's speculative, there's no precedent for those circumstances. Point is, it's a risk, sure, but I believe the worst you can expect is a court order to shut down. But even Paragon Chat runs that risk.
