• Submit bugs, issues and patches to the Haxe issue list.
• Work on Development of a compilation target for Haxe

If you want to make some changes to Haxe you can first discuss them on the mailing list

The source code for the haxe compiler is in Google code:

svn checkout http://haxe.googlecode.com/svn/trunk/ haxe-read-only

Make your changes, prepare a patch, submit it to the mailing list.