He's not even asking that much, so why is it that this repackaging of SpamBayes rub me the wrong way?

So how much does all this good stuff cost?
First off, we give you a month's free trial, so you can train your filter and get a good feeling for how D2S works. After then, we charge a subscription of US$35 per year (rates may vary in other countries). Extraordinarily good value! Plus, we offer a no-strings money-back guarantee if you're not 100% delighted with this service!

He's done quite a bit of work, apparently, moving SpamBayes from Python to Java, and SpamBayes is a PSF-licensed project (it's BSD-like).

So what's the deal? Well, this is where the whole LGPL bit breaks out a bit (or LGPL were there no Java/LGPL issues). If you grab open source code that's doing a very specific purpose and modify it for your own use, it seems you'd feel compelled to give back to the people that did that groundbreaking work. Here, that doesn't seem to be the case. If this guy wanted to turn SpamBayes into a Java lib and give that lib away, then sell a mail server he built on top of it, sure, that's great. But to port an existing open source project and keep those cards close to the vest boarders on immoral [for me] and certainly seems to skirt common courtesy.

Now I could be very wrong on one count and horribly biased on another. For one, he may have just gotten to the core of the formulas/process behind SpamBayes, which he then clean-room implemented in Java. If that's the case, more power to him. Secondly, in the interest of full-disclosure, I want his library!. If either of those deflate my arguement entirely, well, I wanted you to know.

Still, stealing from open source without giving back (heck, even Apple's giving back to BSD) is just plain wrong.