Well, that's a peculiar desire. If a programmer wants to state "I do not want my code to be used in closed-source proprietary software" there's little more they can do than release under the GPL.
There might be some good faith legal consultancy in seeing how, for example, the CDDL and the GPL interact, but for using GPL code in closed source products, the only excuse really is "What can I get away with?"
Well, that's a peculiar desire. If a programmer wants to state "I do not want my code to be used in closed-source proprietary software" there's little more they can do than release under the GPL.
There might be some good faith legal consultancy in seeing how, for example, the CDDL and the GPL interact, but for using GPL code in closed source products, the only excuse really is "What can I get away with?"