[ninkendo]

I have a question about how derivative works are defined with respect to AGPL.

With the GPL, you couldn't distribute software that links (at runtime) to GPL software, without open-sourcing your software as well. This is because, linking another piece of software to a GPL'd binary means you're creating a "derived work". That's why they made the LGPL (the "lesser" public license) which allows being linked to from closed-source works, without being considered a derived work.

With AGPL, they seem to have gone the opposite way from LGPL: it seems to have extended the definition of "derived work" to include software that accesses the covered software over the network. If that's the case, doesn't that mean you just plain can't use MongoDB in the backend your own closed-source website (without open-sourcing your site's code?)

[nebulous1]

I think you're slightly off there. The AGPL doesn't apply to software accessing the AGPL licenced software over a network, it applies to the AGPL software that's being accessed. As in it applies when the software is being accessed over the network rather than when it's being distributed (as with the GPL). This is actually mentioned in the article.

[vishvananda]

I think you have this correct, as I understand it. Just to explicitly state the differences:

1. You can modify GPL code as much as you want, and as long as you don't distribute the software, you do not need to make the modifications available. If you distribute the software, you are required to make your code available.

2. The AGPL extends the definition of distributing the software to making the software available over the network. This means if you modify AGPL software and then make it available over the network (as SaaS, for example), then you are required to make your code available.

[ninkendo]

> The AGPL extends the definition of distributing the software to making the software available over the network

Doesn't this apply transitively? That is, I made MongoDB available over the network to my web tier (thus creating a derived work), and made my web tier available over the network to your browser (thus distributing it), thus, haven't I transitively made a derived work from MongoDB available?

I ask because this exact scenario seems to be what makes the company I work for so scared of AGPL. It's not necessarily cut and dry, but it's a scary enough possibility that we just ban it outright.

[greenshackle2]

Runtime linking doesn't always equals derivative work. Some GPL enthusiasts would like it to be that way but it doesn't mean it is. As far as I know it's a murky legal issue. I forget the exact case but one counter-example was: you have proprietary library A. Someone makes a GPL implementation B with a compatible interface. You ship software C with instructions that users can use either library A or B. An example of this would be BLAS libraries, which have both proprietary and open-source versions. Software C is obviously not a derivative work of GPL library B.

Now, the risk that a court might decide your software is a GPL derivative because it links GPL software might be enough to dissuade your company from using GPL software altogether.

LGPL makes it explicit that you can link against the software without making your software GPL/LGPL so it removes that risk.

And that's not what the AGPL is about. It's not extending the definition of what a derived work is, that is completely outside the hands of the license, it's a matter of copyright law. The GPL says if you distribute GPL (and by extension GPL-derived software) you must distribute the sources too. The AGPL says if a user accesses AGPL (and by extension AGPL-derived software) over the network, you must distribute the sources to that user. It doesn't mean that if a user uses unrelated software to access AGPL software, that unrelated software is somehow derived from the AGPL software.

[int_19h]

> I forget the exact case but one counter-example was: you have proprietary library A. Someone makes a GPL implementation B with a compatible interface. You ship software C with instructions that users can use either library A or B.

Are you referring to the discussion between the author of CLisp and Stallman about GNU Readline, by chance?

https://github.com/JoshCheek/clisp/blob/master/doc/Why-CLISP...

[thawkins]

Also the only part of mongo that is limked is the driver, not tbe database product. All the drivers are licened under apache 2 license, which is permissive, and largly just demands preservation of copyrigths and trademarks. It does not mandate source distribution for derived (linked) products.