[gnud]

As I understand it, with the GPL, you must offer source code under the GPL to everyone you distribute the software to. With the AGPL, the same goes for those that use the software over the network.

So you must offer the source of the database everyone who connects to the database over the network, under the AGPL. But if you deliver a web app, not a database-as-a-service, your users don't connect to the database. And since this database uses the Cassandra protocol, I'd say your web app isn't a derived work of the database in any way.

Of course, that last part is the sticky bit. But if applications using database servers via a well defined protocol are judged to be derived works, we might have other problems - hence the reference to MySql in my first post.

[snuxoll]

Requiring GPL’d software to function means your product is a derivative work, full stop as far as the spirit and letter of the license is concerned. Using it over a network instead of linking against it doesn’t change this, if you depend on MySQL or any of the forks and distribute your software it must be made available under a GPL-compatible license. The requirements of the AGPL become clear in this regard as well; network use is distribution with the AGPL - incorporating AGPL’d software into your application means you must consider your entire application as licensed under the AGPL or compatible license.

MongoDB muddied the waters here by deciding to interpret the AGPL differently, but I wouldn’t risk your business on it.