Just curios, because if it is anything remotely similar to selling commercial products or closed web-services (as most developers here do), you can't talk about trapping users or about the virtues of free-software with a straight face: that's called a double standard.
And most people that do that (according to surveys I've seen) are either still in highschool/college or just hypocrites ... with the occasional "real deal" that manages to live off consulting for open-source development (core project devs mostly) and writing books / training.
http://www.gnu.org/philosophy/java-trap.html