With all respect (as I am very interested and excited by the work being done with Foolscap), I have to ask if it is still accurate to market Foolscap as the 'successor' or 'replacement' for PB.
Fair enough. In the early days (um, 5 years ago? wow), we called this project PB2. I moved it out of the Twisted SVN tree when the development policies began to diverge too far (UQDS vs experimental+fast-moving code). I renamed it to Foolscap at about the same time because of just the sort of uncertainty that you mentioned, and because sticking with twisted.pb2 was an installation headache (namespace packages, etc). At PyCon, the sort of communal marketing position that we seemed to wind up in (i.e. the set of statements that, once uttered, weren't immediately corrected or contradicted by everyone else in the room) was that there's a spectrum, from AMP to PB to Foolscap, in roughly increasing order of featurefullness/size/complexity. While I see places where I'd use AMP instead of the others, personally at this point I don't see any reasons to use PB over Foolscap. But of course I feel more comfortable using Foolscap than anyone else in the world :-). I stopped paying attention to PB tickets years ago, and fortunately more diligent people than me have stepped in and fixed them, so PB is in a better shape than it was before. It still can't do everything that Foolscap can, and is unlikely to, because, well, that's what Foolscap is for. But PB is not going anywhere soon, so if you're intersted in building something that doesn't require anything outside of the twisted tree, and you don't want capability-oriented encryption, third-party references, eventual-sends, adaptor-based third-party serialization, sealers/unsealers, or promises, then PB is for you. I still suspect that Foolscap may find its way into twisted/foolscap/ some day, but I'm not pushing it, and I think it needs to be a lot more mature first (i.e. I need to be content with seeing the rate of change drop drastically, as befits anything under the UQDS discipline). cheers, -Brian