Here is how you can join us.
First, get yourself a working git package on the system where you will be doing development.
Create your own github account.
You may fork/clone the Friendica repository from https://github.com/friendica/friendica.git.
Follow the instructions provided here: http://help.github.com/fork-a-repo/ to create and use your own tracking fork on github
Then go to your github page and create a "Pull request" when you are ready to notify us to merge your work.
Please pull in any changes from the project repository and merge them with your work before issuing a pull request. We reserve the right to reject any patch which results in a large number of merge conflicts. This is especially true in the case of language translations - where we may not be able to understand the subtle differences between conflicting versions.
Also - test your changes. Don't assume that a simple fix won't break something else. If possible get an experienced Friendica developer to review the code.