I would like to correct a statement made here. eZ Systems does indeed provide guarantees for eZ Publish running under the GPL license. This is a core part of eZ Publish Premium: http://ez.no/support_and_services/ez_publish_premium
eZ Publish Premium is a fully supported version of eZ Publish and it can be under either GPL or the PUL license, both with the same level of support and unlimited bug fix guarantee.
Of course it is possible to get support for eZ Publish from you. I didn't mean to claim that it was otherwise. I'm simply more interested in a not having the Premium option in place scenario.