IANAL, but there is nothing stopping anyone from charging for GPL software. GPL, does not mean free, it means that you can get the source code if asked for it. So if I was doing this type of a projects, I would have the source available somewhere and just go on. Now, you might also have to give up the source code of your website/service as well by using GPL code.
This is from the selling FAQ on the
http://gnu.org[
^] site
Actually we encourage people who redistribute free software to charge as much as they wish or can. If this seems surprising to you, please read on.
[snip]
When we speak of ``free software'', we're talking about freedom, not price.