Not a customer and their access agreement isn't public, but terminating a contract in retribution for redistributing their patch would be a violation of the GPL's "no further restrictions" clause and thus they would be in breach. If they're pulling a stunt like that somebody with big enough pockets only needs to file a lawsuit.
I don't think that's true. "If you redistribute we stop collaboration" is not a restriction on the source code the customer has access to.
I think this clause doesn't mean what you mean. This clause means that the GRSecurity project can't license their modifications under a more restrictive license than the GPL. Which the GRSecurity project respects, customers do have access to the modifications under the GPL license.
