yes you can. It's open source so it means that you can and are allowed to edit anything you want to. Also releasing it to other people shouldn't cause any problems, since there are no copyrights. (at least I don't think there is)
But as already said it would probably be best to contact people behind the distro you are going to build your own distro on top of. And also you might want to ask them if they want you to mention that you used some of their stuff in the distro. (not that it would matter so much, but I believe they deserve some credit since they designed the thing you have based you distro on)