The best way to get involved with the development is to check out the most recent code, modify it to work the way you'd like it to work, then commit your changes to GitHub, so the lead developer can pull in your changes.
Most Recent Code
The most recent code can currently be forked at GitHub. Since phpfreak has been the most consistent developer since mid-2008, you could probably start with his repo, and merge any of the commits anyone else made, if they make sense.
Things to Remember when Modifying Code
- Try to keep your commits small. A commit for "Order the list of company users alphabetically." is probably going to be easier to merge in than a commit for "Re-arranging a slew of things in the UI"
- Try to keep your commits to the point. If you want to re-format the code to conform to the coding standard, and also make changes to the functionality, do two separate commits - one in which you can make the cosmetic change to the code, another in which you change the functionality.
- If you're changing the UI, your changes should probably mostly be contained to the theme. It will be easier to convince the lead developer to add those few functions your theme needs than it will be to convince them to change the whole UI. See https://github.com/dbernar1/kampPro2 for an example of how to do that.
- If you don't already have one, get an account on projectpier.org (you'll need this for the forums and issue tracker) You can also enable the contributor links block for a handy tool
- If you are not interested in contributing to the code base, look at the other ways on contributing to the project
- Check out the issue tracker for bugs, tasks, feature requests and see if you can help. Also, if you've found a bug please read the bug submission guidelines.