Here are the FAQs to the SSPL.
However, Atlas will allow you to use MongoDB without the need to worry about the SSPL.
The enterprise license is expensive (IMO as a startup). Which is why I went with Atlas. M10 cost me around $60 a month.
When I contacted MongoDB for more info about the community license use, this was the answer I got. At first I did not like paying so much for the DB; however the whole infrastructure is run by MongoDB and now I have one less worry every month. And I can focus on the application now.