Do I have to distribute my commercial source code that links GPL software if I only use this commercial software to provide a reporting service?

Question

At my company we created proprietary software that we use only internally - we do not distribute this software - to generate reports from client data. We sell these reports to our clients, not the software.

If we were to link to GPL licensed software from our software, would will still need to (upon request) provide our proprietary source code?

I understand that if we distributed our proprietary software itself, the answer would be yes. And I understand that if we used the proprietary software only for internal purposes, the answer is no (e.g., see discussion here). But if we only use the proprietary software internally, in order to generate a report product that we do sell (distribute) to customers, then what is the answer? This link seems to suggest probably not, but what if the GPL software creates a particular image that is displayed on one page in a many-page report?

Thanks in advance for some clarity on this. Legalese is so hard for me to understand, but if you could also point me to the particular sections of the GPLv3 that make this clear, I'd appreciate it.

Answer 1

For the regular GPL, the answer is no. Quoth the FSF FAQ:

Q: Is there some way that I can GPL the output people get from use of my program? For example, if my program is used to develop hardware designs, can I require that these designs must be free?

A: In general this is legally impossible; copyright law does not give you any say in the use of the output people make from their data using your program. If the user uses your program to enter or convert his own data, the copyright on the output belongs to him, not you. More generally, when a program translates its input into some other form, the copyright status of the output inherits that of the input it was generated from.

In this case, you are the "user" of the GPL'd program, so the output is all yours.

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It's worth mentioning that if we were talking about the AGPL, and your clients were "interacting with [the software] remotely through a computer network", then the answer would be very different. But it sounds like neither of those conditions apply to your case.

Answer 2

The fact that a tool was used to produce some output does generally not give the copyright holder of the tool any rights to the output to the tool. For example, Microsoft has no rights at all to the documents that you create with Microsoft Word.

There are some rare cases of tools where copyrighted parts of the tool are included in the output. That's very rare. Obviously you can check that with your documents. If the software prints "Page 1" nobody would consider that they have a copyright on that, even if the "Page" is the direct copy of the word "Page" somewhere in the copyrighted source code.

There are applications with licenses that restrict use of the output. An example was a quite successful compiler for MacOS which came in a paid version and a free version for students - both versions were identical, except that the free version explicitely did not allow making money from the output of the compiler. So you could use the free version to build a product, but when you sold it for millions you had to buy the paid version.