I was contacted by one of the developers of the open source screenwriting
program Trelby (which is, as WikidPad, built with Python/wxPython) because they
want to create Mac OS port.
Personally I couldn't help very much but maybe some of the readers with Mac and
wxPython experience can and want to help. If so, please have a look at
http://www.trelby.org/contribute for details.
Michael