How exactly is the unresolved tension keeping things in check? The untested nature of how far the GPL can hold up in court is exactly why we see violations of the GPL so flagrantly. It's exactly why violators of the GPL are willing to let this go to court (if there was ample precedent of the GPL being upheld it is reasonable to assume most corps would choose to settle issues like these before they escalate to a law suit).

If the GPL is never proven to be upheld (at least to the point where most legal corporate accepts it) by the courts then it is a meaningless licence that only matters to free software advocates and geeks.