The failure of either party to enforce any of the respective rights or remedies hereunder, or to promptly enforce any such rights or remedies, shall not constitute a waiver thereof nor give rise to any estoppel against such party nor excuse any of the parties hereto from their respective obligations hereunder. Any waiver of such right or remedy must be in writing and signed by the party to be bound and must expressly state that such right or remedy has been or thereby is waived. This License is subject to enforcement at law or in equity, including actions for damages or specific performance. Time is of the essence hereof.