You have done a good work on the skin. However, I find it lacks an accompaning license. The terms at http://www.rilnet.com/skins/commercial-version also make it more confusing, as it seems to be unfree. Still, as you're linking against MediaWiki (and even derivating code from it), it should be GPL. You can still sell or provide it for free to whoever you want, but the lack of GPL notice on the copies is in itself a GPL violation.