The title made me think you were going to fork the Open Sound System (OSS) Anyways, you should probably read the license of what you're forking, but in general

The title made me think you were going to fork the Open Sound System (OSS) Anyways, you should probably read the license of what you're forking, but in general it should be OK to just fork it and give credit to the person who made the original. Again, though, read the license. Also, it's probably a nice thing to do to contact the original developer and tell them you're forking them.