One big feature that now exists is that anyone can create fork the uPortal git repository, make some set of changes on the fork, and then request those changes be pulled back into uPortal. Think of this as "submitting a patch" on steroids. For anyone that is interested in learning more about git the links in the Additional References section below are quite valuable.
A proposed workflow for the project and documented in the wiki: https://wiki.jasig.org/display/UPC/Git+Workflow
There are a few workflow options, the direct merge option is only applicable to uPortal committers but the Pull Request option is applicable to committers and anyone else that is interested in supplying patches to uPortal via GitHub Pull Requests.