Updated can be found here
Github is the source control repository for all OHDSI projects.
Here is the main URL for OHDSI Github projects: https://github.com/OHDSI
OHDSI developers use Github flow with the fork and pull collaborative development model.
Here is a good "Hello World" example but note that in the fork and pull model, unless you are the project maintainer, you will need to first fork the project master branch and then create a new branch for your change on your forked copy. Your pull request then triggers the project maintainer to merge your forked project branch back into the main project master.
Additional info on the fork and pull model of collaborative development
If you develop on Windows, you can download the Github for Windows Client. There is a good Windows Github client guide with helpful info on cloning repositories and branching locally using the Windows client.