To be clear, it's not yet known for certain if the chilling effect of a terminated contract violates the "no further restrictions" clause of the GPL or not. Evidently IBM's lawyers think it doesn't. But it would be good to test it in court first.
More importantly, IBM has the best of the best in terms of lawyers. The likelihood of them ever losing a case is basically nil. They sustained and won a proxy war with Microsoft, when Microsoft was the richest company on the planet.
