I'm having a tough time trying to figure out the best way to handle this. I've created a few themes last year, released them under a GPL license, and pretty much forgot about them. My goal was to put them out publicly as samples of my work.

I've recently come across a site and was shocked they are selling one of my themes among several other themes (not mine) and other support and package systems. Anyway needless to say I'm not happy about this. I did not intend for those themes to be sold, and if they are to be sold, at least I would expect a percentage of those sales.

I contacted the website asking how many they sold and that I'm the author of one of the themes they were selling. I eventually received a reply that my theme is a GPL theme and that this license allows them to sell it without compensation to me. WTF? Just the way the reply was worded pissed me off.

There is no way to comment on the site to inform possible buyers that those themes can be downloaded from my site.

What can I do about this? I realize now it was a bad choice to release them under that license. Is it possible to take back the theme from public distribution or is it out forever. Can I change it from GPL to another license at this point? Will that be sufficient to stop the sale of my theme in the future? Any insights are appreciated.