Via slashdot, I came across this GROKLAW article that explains in detail how there is no way you can be forced to open the source to a proprietary program that has been linked with GPLed code. FSF’s Eben Moglen is quoted in the article:
The claim that a GPL violation could lead to the forcing open of proprietary code that has wrongfully included GPL’d components is simply wrong. There is no provision in the Copyright Act to require distribution of infringing work on altered terms. What copyright plaintiffs are entitled to, under the Act, are damages, injunctions to prevent infringing distribution, and–where appropriate–attorneys’ fees. A defendant found to have wrongfully included GPL’d code in its own proprietary work can be mulcted in damages for the distribution that has already occurred, and prevented from distributing its product further. That’s a sufficient disincentive to make wrongful use of GPL’d program code. And it is all that the Copyright Act permits.