I hope you find Hex Fiend useful for whatever purpose, but if you are interested in contributing changes on an ongoing basis, I'll be happy to grant Subversion commit privileges to some interested developers who submit quality patches. There is a wiki aimed at developers accessible from the page, but daily builds, mailing lists, or discussion boards are also a possibility. You can contact me at the e-mail address at the bottom of the Hex Fiend page if you are interested in any of these.

Version 1.1.1 has some important bug fixes (see the release notes), so you should upgrade even if you are not interested in the source.