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Comment by netr0ute | Hacker News Reader

Why is the AGPL such an issue?

It depends if you find it acceptable that the work you created gets assigned the AGPL license. However, this problem was already solved at this point, so it's a non-issue these days.

One practical problem, even for developers who are fine with licensing their code to whatever open source license is easiest, is that not all open source licenses are AGPL compatible. Take for example the Mozilla Public License, which is inherently incompatible with AGPL because of the terms imposed; this means that any project using MPL licensed libraries could no longer be linked with Mold.

License incompatibilities can be a huge pain (see: ZFS + Linux). If you develop software for yourself this isn't a problem, but if you intend to distribute your software this becomes more of an issue.

This is probably also the main reason why normal linkers/compilers don't impose licenses on the produced work.

It's not an issue for linking AGPL code.

The issue was that they wanted to claim that AGPL was contagious - That by using mold, your outputs would also be required to become AGPL.

Normally the tools people use don’t dictate the license they must use for their code.

The point of copyleft is to dictate the licence you must use, if you wish to (roughly speaking) link with the copyleft-licensed work. There are plenty of libraries that you cannot use if you wish to distribute your program without making its source-code available.

The unusual thing here is that the creators of a linker are apparently trying to have the copyleft licence propagate to code that is input to the linker. Others have pointed out that GCC has exceptions for this kind of thing, despite that it is released under a strong copyleft licence (GPLv3+).

No, the point of Copyleft is for you to not restrict the freedoms you got when you used the software when distributing it to others. You can use Copylefted software in any way to your heart's content in combination with whatever other software you want, you can just not distribute it using a more restrictive licence.

This level of detail is incidental to my point, hence roughly speaking. Even the GNU folks summarise copyleft essentially as I have. [0]

Also, your account of copyleft is still incorrect. It's true of the GPLv2 and GPLv3 licences but not true of all copyleft licences. The AGPLv3 licence, which is the one relevant here, doesn't apply only on distribution.

[0] https://www.gnu.org/licenses/copyleft.en.html

edit I think I was mistaken in putting propagate to code that is input to the linker, though. As lokar's comment points out, it's instead about the output of the linker.

It's not, if it's contained to just the linker itself (which it is now), that's not why I stopped using it. I did so because it seems like they don't understand that much about AGPL and licensing in general and could change their license terms at any point to say something like "we claim AGPL propagates to the linker's output" which is very legally tenuous itself to claim so.

Tenuous or not, I believe GCC explicitly has a licensing exception that states that compiler output is not considered a derivative work of the compiler, and thus must also be licensed under the GPL. So the GNU/FSF folks at least thought it was a concerning enough legal idea to explicitly account for it.

Not sure we can say that a linker is the same as a compiler in this sense, but if so, maybe it is indeed worrisome.

It does not look like binutils (including ld.gold) has that exception[0], so I don't think the FSF would agree.

[0] https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=READ...

If I recall correctly it is the standard libraries(such as libstdc++) that need this exception and not the compiler itself.

That exception exists because compilers have a tendency to leave little bits of itself in code that they compile. For example, if you're compiling to a target that doesn't have a division instruction, you're going to be using a compiler-provided division routine that gets combined in with the source code. And that routine is a clear part of the compiler's source code.

The standard compiler license exception (this applies to LLVM to, e.g.) says that any such code that gets combined in with your application code doesn't count. Note that it's still a potential license violation to use that code elsewhere (say, using those routines in another compiler).

This isn't a concern for linkers because linkers don't really provide anything in the way of code, everything being provided by the compiler as a compiler or language support library. The largest code it might add to your program is probably the PLT stub code, at best a couple of instructions long.

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