I also open-sourced Inkpad, my iPad vector illustration app, a few weeks ago: https://github.com/sprang/Inkpad

I'm planning to submit this version of Brushes to Apple within the next week or so. There are still a few outstanding issues.

If you'd like to contribute, I'd appreciate bug fixes, new features, and localizations for your language of choice. Otherwise, I hope you can learn something from it, or find bits and pieces that are useful in your own apps.