Wooden Brain Concepts today released an update to OmniGrowl which really, truly, fixes the trial expiry at launch bug.
Unregistered users were seeing a trial expired message immediately after launching OmniGrowl. The intent is for OmniGrowl to be fully functional for 6 hours of use per launch, regardless of whether it is registered or not.
Last week we released a Mavericks compatibility update that we thought had also fixed that bug. It turns out that OmniGrowl was still evaluating trial expiration relative to the application build time, not the launch time. It was a silly error on our part. This should now truly be fixed and we apologize for the inconvenience. Please contact us if this still occurs on your system.
As usual, please refer to the version history for details.