I really like the card. Being a Terminal, it involves quite a bit of strategy the fact that you may get it without buying it. We are only used to get dead cards or Coppers against our wills, not terminals (Swindler, Ambassador and Jester may give out unwanted terminals, but with Swindler and Jester is usually only once in a while and with Ambassador is rare).
I would consider make it go to the player on your left at clean-up instead, just so you have it in play like normal actions through your turn (seems like it may cause strange interactions and lose track considerations, like Mining Village). It will also be clearer when you TR or KC it. Also, maybe trash it or return it to the supply first (for instante, what happens with the Traitor if the player to the left reveals Trader? Ambassador solves it nicely by letting it in the supply, and Masquerade does not involve a gain, so there is no Trader possiblity).
I strongly agree it needs some resource, more importantly, I think it needs to be coin (+$2 sounds fine). Otherwise, after the curses run out, this is almost like a dead terminal you want to give to your neighbor. The problem is, with Cursers like Sea Hag, the Curses eventually run out and you will not buy any new Sea Hag (barring edge cases that are of no interest). In this case, however, you can have a sort of stalemate situation of 10 Traitors going round and round with nothing else going on (especially in 2p, where 5 Traitors per player + 5 curses each is a lot of dead cards). If the Traitor gives +2, while you pass it, even without Curses, it will probably let you buy at least a Silver and make the game alive again. Also, you may consider some way of trashing the card if there is no Curse-giving.
I would price it at $4 to avoid opening double Traitor. I think that gives too much swingyness and first player advantage, possible putting 4 unwanted cards into the other player deck. Getting hit twice before the 2nd reshuffle by a double-Swindler or double-Ambassador opening is already really awful. Priced at $4 makes it slower for the Traitors to flood everyones deck. I think power attacks are nice, but is also nice that you can defend from them to some extent, at least in some boards, to allow diverging strategies, which are much more fun than mirrors. This considerations seem even worse for 3p, as one player getting Traitors means everyone will be getting them really soon, so there better be some barrier preventing doing that too fast.