@unfa I only know of Magic UV, which comes bundled within Blender. By the way, there isn't proprietary add-ons for Blender. As far as I know, they all must be GPL-licensed, because they use Blender's code and inherit the license. So, if you buy an add-n, you have the right to view and modify the source.
(I know that technically, there can be proprietary add-ons for Blender, but they can't use any of Blender's code, so nobody does it).