They aren't. Those are the Revolutionary Communist Party, USA. These guys are the Revolutionary Communists of America. Two completely different, unrelated orgs.

I'm in the PSL and I recently started meeting regularly with a couple guys from the local RCA. Their organization is not perfect but they have been friendly and enthusiastic about cooperation and I look forward to working with them. Here's some of what I've learned either from them or the PSL:

They're a continuation of a Trot party, Marxist International (that changed its name at least partially due to a sex pest scandal), but they claim to be "non-sectarian Marxist-Leninists" and not Trots. The local guys seem unaware of the history of their party, they joined two months ago along with the name change and believe that the party is new and was founded two months ago.

I've re-written this paragraph several times because I don't want to come off as too harsh, because they really are good folks who are doing their best, but: their organization suffers from a lack of, well, organization, and a focus on what I believe to be ineffective tactics ("agitation", selling newspapers on street corners, etc.). They are also admitted class-reductionists, and the local branch at least is seven or eight white guys and one of their girlfriends. They've read a lot of books but knew very little about the political struggles going on in their own city.

The only time I would suggest joining the RCA is if you've already tried to join your local PSL branch and haven't heard back.