Some of us prefer others to voluntarily give back rather than be forced to.
This statement has always confused me. Nothing in the GPL requires anyone to "give back" anything. What it requires is that if you give a GPL-ed program to somebody, you must give them (and only them) the source code to that program. Modifications to the source code must be distributed with the original code under the same license. So if you modify a GPL program and give it to a somebody, they get that code and all the rights to it that are protected by the GPL. You need not give it to the entity that originally wrote the GPL-ed code.
"Conversion, fastidious Goddess, loves blood better than brick, and feasts most subtly on the human will." -- Virginia Woolf, "Mrs. Dalloway"