not bad...
I remember in 2003 ICQ went after some domains and got them, dont remember which ones, but they got them by having the owners surrender them, not by WIPO/UDRP.
assuming they do not go after you, it should be relatively easy to setup some forum.
hard to put a value on it, and icq has been around a long time so I dont see it going away anytime soon.
throw a forum on it and see what happens.