Haven't githubs new interface made it almost impossible to investigate what a developer has written? For example, on my profile page I have 32 repos. But 29 of them are forks of other projects which I haven't added anything to.
It's somewhat imperfect as not all forks or mirrors are marked as such by github (if, say, it's a fork of a repository not originally hosted on github), but it works in the vast majority of cases.