If the code was legitimately released under an open license (which is, admittedly, a potentially-very-large "if"), then the open-licensed versions are out there and there's not much that can be done about it, as the license allows anyone who has the code to redistribute it, including putting it back onto CPAN. The owner can choose to release new versions only under closed licenses (or to not release them at all), but the cat's out of the bag on the open versions and the best you can do is to fork the code into separate open and closed versions.
If it wasn't legitimately placed under an open license, well... you may find yourself in need of a very good lawyer once they realize that you released code you didn't own and claimed that it was licensed under terms you weren't authorized to offer.
