You want to contribute to Gajim and help in development? Here's a list of things you should do:
Get in touch:
Go to firstname.lastname@example.org, that is our conference room. You can always ask for help and talk about Gajim there.
Report bugs and share your mind about Gajim
Get in touch with development:
Get the development version of Gajim. Install mercurial (either a console tool or one of the gui wrappers, like tortoisehg) and download Gajim sources using it.
Make a jabber account specially for testing. It will be easier to test things if you will use a small jabber account without all your friends. You will also less annoy them ;-)
Create a different profile with that account. Use gajim -p test or ./launch -p test and set up all things.
gajim -p test
./launch -p test
Read our Coding standards.
Just start! There's plenty to do, you can see all [report:3 open tickets], also you can think of a new feature not already listed.
Check out embedded IPython interactive shell - it should help you familiarize with source code.