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.