I've just uploaded py2app 0.5 and new versions of altgraph, modulegraph and macholib. I hope this solves most issues with py2app. "easy_install-X.Y -U py2app" should install the software for you (where X.Y is your favorite version of Python)
There is one new feature in this release: experimental support for python 3. This basicly means that I managed to build a single application as a standalone application bundle, without much testing. Alias builds and plugin bundles almost certainly don't work (the first because alias builds use the Carbon module which isn't available in python 3, the latter because I had to rewrite the C code in the application bundles and probably have to do the same for plugin bundles).
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