Small-scale document NoSQL

I need some advice because the Internet is bringing me to confusion. If you were to make a small website (scaling is not a requirement), which needs a document NoSQL database, which one would you use. The DB should have Golang drivers.

I'm asking this question, because I see 1 choice really, and that is MongoDB but if I use MongoDB, as far as I understand it, I'll have to open-source the project because of licensing, even though the website client-facing bit could be even made statically hosted.

Seems like most companies are logically building for scale but I need to remain small-scale, and low-cost. I don't want to "build my own" because I'm not familiar to the fundamentals of NoSQL either. I just want to learn it and use it, simple.

P.S. At some point I looked into key-value DBs like RockDB, Badger, BoltDB but I think there's a risk that this would make the cost of hosting of the website go up, redundantly. Hosting services often allow low RAM - 1GB, for low-tier plans and I'll be aiming to keep the website minimal to fit there.