Constraints and continuations comment 000
I don't think Twisted's use of continuations looks much like Seaside's. Twisted is very explicit about where a continuation is formed and returned (via Deferreds), while in Seaside it is entirely implicit. CherryFlow is the only system I'm aware of that does Seaside-style continuations (using Stackless).
I should amend that -- Twisted's Athena probably is more like Seaside, though (I only know about them indirectly). But I also presume Athena is strictly for the web.
Athena is a Divmod project, and has very little to do with Twisted (other than the fact that it uses it as a library).