Welcome to the MongoDB Community Forums @jay_87395!
Use of Ops Manager is subject to the MongoDB Customer Agreement. The most relevant clause for your question is 2 (b) regarding Subscriptions:
Free Evaluation and Development. MongoDB grants you a royalty-free, nontransferable and nonexclusive license to use and reproduce the Software in your internal environment for evaluation and development purposes. You will not use the Software for any other purpose, including testing, quality assurance or production purposes without purchasing an Enterprise Advanced Subscription. We provide the free evaluation and development license of our Software on an “AS-IS” basis without any warranty.
If your environment and usage meets this criteria, you can use Ops Manager (and MongoDB Enterprise) without purchasing an Enterprise Advanced Subscription. Any other usage would require appropriate licensing.
Regards,
Stennie