This exists in Git and Github accommodates it just fine. See [0] for the following explanation:

You may be wondering what the difference is between author and committer. The author is the person who originally wrote the patch, whereas the committer is the person who last applied the patch. So, if you send in a patch to a project and one of the core members applies the patch, both of you get credit — you as the author and the core member as the committer.

Try it by setting the author on a commit you make. Github displays it just fine. I used to use it in school when working with non-comp-sci students on collaborative work (for instance, a report written in LaTeX).

[0] http://git-scm.com/book/en/Git-Basics-Viewing-the-Commit-His...