Thanks for contributing to Twisted!
A couple of things with regards to your questions and your project in particular:
About the licensing issue: well, Twisted itself (as you probably already know) is released under a permissive license, and that's a conscious decision. The GPL can make it somewhat harder for companies to use and potentially contribute to your code. Plus, your code is a library, not a standalone app, which is an argument for a more permissive license. If you *like* the GPL's copyleft bits, by all means: please continue using it (just be aware that means quite a few people will refuse to touch your code). Ideally, there'd be a license identical to Twisted's.
Something that might be slightly more important: do you have a public VCS repository somewhere (Launchpad, Github, Bitbucket...)? The people you would want contributing are probably very scared of hacking on an existing codebase without the ability to branch/fork and later merge again :-) An additional problem is that there's no obvious way to report bugs, which might scare people out of using it.
Somewhat related to the last question: you might want to consider registering your thing in the Twisted Community Code (tx) group on Launchpad for free advertising:
Lots of luck with your library and the app that presumably goes with it (albeit a bit more under the radar ;-)), Laurens