So you want to help out with Geeklog development? Excellent! Here are the first steps to get you started:
Next, try the development version. You can either use Mercurial or download the nightly tarball. In either case, you need the PEAR classes, which are not included in Mercurial or the nightly tarball (more detailed instructions here).
Once you got the development version up and running, you should read Alan McKay's excellent Beginner's Guide to Geeklog Programming, which will explain to you how to do things the Geeklog way.
We also recommend you have a look at our Coding Guidelines. Summary for the impatient: We're mostly following the PEAR coding standards.
Dive into it
Once you have a rough idea how things work, try browsing our bugtracker. Pick a bug that interests you. Try to reproduce it. If you can add any useful information to the bug (e.g. steps to reproduce the problem), go ahead and leave a comment.
See if you can find the area in the source code where the problem occurs. Try to think of a way to fix it and either fix it (patches are always welcome!) or, again, leave a comment.
Don't worry, not all the open bugs are hard. Some are fairly easy and are only open because nobody had a chance to fix them yet. Even if you can't solve the problem, you'll learn a lot in the process.
(to be continued ...)