I do believe there is an explicit rule stating that you cannot use someone else's skin as a base skin for your own. They probably crack down on that more than they do on Honeydew skins, because no one diamonds honeydew skins anyway . In the case of Teen skins, it's hard to prove that they are stolen because there are so many of them. It would take longer than it is worth to find the originals.

If you use a base, get express written permission from the original skin maker, and post it along with your skin. That should increase your chances.