Since a few years the license of MongoDB has changed and is not a Free Software (or Open Source) license anymore,
see https://en.wikipedia.org/wiki/Server_Side_Public_License:
the SSPL is not recognized as free software by multiple parties, including the Open Source Initiative (OSI) and multiple major Linux distributions
https://en.wikipedia.org/wiki/MongoDB#MongoDB_Community_Server_2
As of October 2018, MongoDB is released under the Server Side Public License (SSPL)
As the MongoDB is an essential component of factile, the full solution is not Open Source (with all drawbacks).
Maybe a different database that is Free Software can be used instead.