recurry:
So, technically, he's in violation of the GNU license as one cannot charge for source code if it's under the license. I think it's ok to charge for one's work but only if one is upfront about it and claims that's what he's doing. Saying that it's a "donation" and that it's "free" software under the Gnu license and then requiring payment to download is not compatible. It's not free, it's a one-time license fee.
recurry, please read the following article from the GNU oganization. You misunderstand the GNU GPL license completely.
Directly from the GNU Free Software Foundation:
Selling Free Software - GNU Project - Free Software Foundation <--seriously, read the whole article.
"Many people believe that the spirit of the GNU Project is that you should not charge money for distributing copies of software, or that you should charge as little as possible—just enough to cover the cost. This is a misunderstanding.
Actually, we encourage people who redistribute free software to charge as much as they wish or can. If a license does not permit users to make copies and sell them, it is a nonfree license. If this seems surprising to you, please read on."
...
"Since free software is not a matter of price, a low price doesn't make the software free, or even closer to free. So if you are redistributing copies of free software, you might as well charge a substantial fee and make some money. Redistributing free software is a good and legitimate activity; if you do it, you might as well make a profit from it."
I've done prob. a dozen hrs of reading about licenses over the last couple yrs, to make sure I fully understood and was in compliance. If you have any other questions I'll do my best to answer them.
~GS