Go ahead and fork, and send pull requests back.
If you modify my examples to suit your hardware/needs, i'd prefer you create an entire new folder that starts as a copy, and modify that. If you're fixing bugs, you can do that in my code so i can take advantage too.
If you just want someplace to put your examples, that's fine too, create a new folder, and put your code and a README.md there that explains what it is. only upload your own code though. If you reference things from an arduino libary, let the arduino tools install/etc that library, don't re-host it.