MongoDB is a popular documents-oriented database, the source code of which is licensed under an open source license, the Server Side Public License (SSPL).1
The SSPL is based on the Affero General Public License v3 (AGPL). Until 2018, the AGPL applied to MongoDB source code. AGPL was replaced with the SSPL in response to cloud hosting providers like Amazon making use of a MongoDB clone as a service. The only meaningful difference between the AGPL and the SSPL is the copyleft provision.
AGPL has a copyleft provision that requires the source code of modified versions of the licensed program be made available to all users who interact with the software over a network. That is, if you modify the program and use it in your cloud-bases application or service, you must make those modifications and the program itself available in source code form.
Mongo replaced this copyleft provision with a new version—copyleft on steroids.
