MongoDB positively asserts that a program that uses a MongoDB database does not form a combined work with it. This is nice because my web service that uses MongoDB does not need to be licensed under the AGPL.
If you modify an AGPL program and make it available to users over a network, those users are entitled to a copy of the modified source. Certainly, if I make a a modified version of MongoDB and deploy it as a public-facing network service that anyone can connect to, I need to make the source available to its users.
However, if the only user directly connecting to my modified MongoDB instance is my web service, but that Web service is public-facing, do I need to make the modified MongoDB source available to the users of my web service? Again, MongoDB has asserted that my use of MongoDB in this way does not form a combined work with my web service. Does an end-user's indirect "use" of MongoDB through my web service constitute "interacting with it remotely through a computer network" as specified in the AGPL?