You can review the specific terms of usage for MongoDB Enterprise in the Customer Agreement applicable to Enterprise downloads.
I believe the relevant section you are looking for is 2(b):
(b) 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.
You will have to ascertain whether your usage is complaint with the full terms of this agreement.