They can't because by definition, restricting end user usage means the license isn't either Open Source or Free Software.

That's incorrect. The AGPL is considered Free Software by the FSF even though it clearly limits use of the software.

If you want to know why they support a license that violates freedom zero you will have to ask them but to me it suggests that the foundation of Free Software is fundamentally flawed in a world of networked software: i.e. the four freedoms are not compatible. My right to exercise freedoms 1, 2, and 3 limits your freedom to exercise freedom zero. Currently software authors have to pick one side of that argument either by using AGPL (restricts freedom 0) or GPL (doesn't protect freedoms 1, 2, or 3).

> it suggests that the foundation of Free Software is fundamentally flawed

Please stop spreading FUD about Free Software. The AGPL does not restrict usage. See Section 13 - the requirement to offer to network users only applies if you also make a derivative work by modifying the software, and even then it only requires you to offer the corresponding source to the work that was modified with the new modifications.

It's not FUD, it's an awkward reality. The FSF themselves don't deny that there's a contradiction. The right to use modify code privately is one of the four freedoms, so your insistence that the AGPLv3 violates it is just supporting the existence of a fundamental contradiction.

This is from the legal analysis by Eben Moglen & Mishi Choudhary for the Software Freedom Law Center[1]

>Whether to extend the copyleft concept to the delivery of services by free software over a network is a complex issue long discussed in the free software community. Freedom zero requires that any user be allowed to run any program for any purpose, which of course includes the provision of computing services to others. Freedom two requires respect for the right of private modification. Their combination requires that anyone be able to run privately-modified copies of GPL’d programs for the purpose of providing computing services to others.

That's very clear that freedom zero and freedom two necessitates allowing people to run modified GPL programs on servers without making the code available to users. The AGPL is explicitly designed to prevent that, so it's inevitably in conflict.

>even then it only requires you to offer the corresponding source to the work that was modified with the new modifications.

As I demonstrated in my other comment the language in the AGPLv3 is identical to the GPLv3 when it comes to the issues of derivative works/combined works/aggregate works. Everybody accepts that the GPLv3 requires software linking to a GPLv3 library to be made available under the terms of the GPLv3. The same applies to the AGPLv3, so in many cases it will mean people will also have to release their own code that links to the AGPLv3 library they are running on their server, if they make modifications to the AGPLv3 code.

[1] https://www.softwarefreedom.org/resources/2014/SFLC-Guide_to...

Anything licensed under the AGPL attaches conditions to using the software. Running the software on a server means you are required to open source the other software running on the server.

That's bullshit. Only if you've made a derivative work (e.g. by linking AGPL software into your software) you have to offer the derivative work under AGPL. You can perfectly well run an AGPL webserver and not be forced to put your operating system under AGPL.

Sure, if you run a server that's only running some unmodified AGPLv3 software then you don't have to share the source, although in that situation the user typically has access to the source through other channels anyway (the market for selling private AGPLv3 code is pretty much non existent, so the code is almost certainly from a public project).

In the real world people typically want to use code as part of their own service/application which contains domain specific logic they wrote themselves.

>You can perfectly well run an AGPL webserver and not be forced to put your operating system under AGPL.

Because the GPLv3 and AGPLv3 (the licences are identical in this regard) have explicit sections excluding operating systems and system libraries from the terms of the licence.