Affero not harmful

Ok, let me quickly recap what several lawyers told me.

First, enterprise MongoDB has a special commercial license for the DATABASE itself. Not just for additional tools. Consequently, contributing to MongoDB requires copyright assignment to Mongo ( https://www.mongodb.com/legal/contributor-agreement ).

Next, let's talk about AGPL. It poorly defines what "derived works" actually are, just as regular GPL licenses. However, there are some guidelines (including from the FSF itself). In particular, if a program uses internal structures of another system, is tightly bound to it and works in the same address space then it's pretty certain that it's a derived work and GPL applies.

In case of MongoDB most real databases will have views, map/reduce queries and other code that fit these conditions perfectly. So their code can be considered a derived work of Mongo and will have to be disclosed as per AGPL if its output is used (for example) to render HTML pages.

This is clearly insane. So MongoDB has a public interpretation of the license that excludes normal database users from AGPL's reach. But they are free to rescind this interpretation at any moment - it won't be retroactive but any code running within future MongoDB versions won't be protected from AGPL.

And before people start telling that "but Mongo queries are just like C code being processed by GCC" - they are not. They are more comparable with GCC plugins and FSF's opinion is that they must be GPL.