AGPL revisited: how MongoDB licensing differs from MySQL

Now that the Affero General Public License (AGPL3) is actually being used by successful projects, I'm looking at it again. Specifically, MongoDB is AGPL3 licensed, and it is being used for commercial applications. But how?!? I though the AGPL was complete communism, and that's what excited me so much about it - one touch of the the brush, and the whole batch of milk is stained vermillion, and your entire enterprise now belongs to Richard Stallman so he can use it to fund GNU HURD.

The AGPL actually has some pretty fixed boundaries:

A compilation of a covered work with other separate and independent works, which are not by their nature extensions of the covered work, and which are not combined with it such as to form a larger program, in or on a volume of a storage or distribution medium, is called an "aggregate" if the compilation and its resulting copyright are not used to limit the access or legal rights of the compilation's users beyond what the individual works permit. Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate.

Upon reflection, the AGPL isn't as restrictive as I once thought. Let's take what I consider to be the most successful GPL (v2) product: MySQL*, and consider what would have happened if it had been released under AGPL instead. Since Amazon used MySQL code to build RDS, under the AGPL Amazon would be forced to release the code they use to provide the RDS service. They would not be forced to release the code for Amazon.com** however: that would clearly be outside the boundaries set out in AGPL.

Also consider that Facebook uses MySQL internally, with something like 4000 MySQL databases to power much of their site, and they've made many changes to MySQL in order to make that possible, some of which they've made public. If MySQL had been AGPL-licensed, they would have been required to make those changes publicly available under the same license.

Google is also reportedly one of the largest users of MySQL, and in a similar spirit they have released some of their tools. However, they released these tools under the more permissive Apache 2.0 license: if MySQL had been released under AGPL3, Google would most likely have been forced to release these tools under AGPL3 as well.*** And now that Google is also offering Google Cloud SQL made with GPL-based MySQL, they don't have to share their work as they would if MySQL were AGPL3-based.

All of this to say: if you want to use MongoDB to power a web app, have fun: the boundaries within the AGPL3 are there to help you, and probably won't require you to hand over your code to every visitor. However, if you see MongoDB and think "hey, that's cool, I'm going to offer a web service with the MongoDB API and become a cloud provider of NoSQL data storage, just like Amazon SimpleDB" then you will have made a derivative work, and you'll have to share those changes with the world under AGPL3.

Finally, IANAL, not in any jurisdiction, and if you base your legal strategy on lay analyses found on personal blogs, then sadly you're not alone and you're in very risky company. Best of luck, however, in finding a copyright attorney who will dig through these issues for you and give you an opinion for less than $500k.

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* The Linux kernel is more widely used than MySQL, but it's so mixed up with other licences that it can't just be GPL anymore, not honestly - and the copyrights are owned by so many different people that nobody can claim ownership. MySQL, on the other hand, was always extremely diligent about maintaining ownership of every line of code they include in their distribution (which made acquisition by Sun and Oracle all the more attractive).
** ... that is, provided Amazon.com was built using MySQL, which it isn't AFAIK.
*** They could still licence their code any other way they want, as they own it, but they'd be required to license it under AGPL3.