Huh, I never really thought about it, but I guess that's one thing that GPL kinda fails at: if your server does all the work, you can leverage open source technology to do all sorts of stuff for your clients, so long as all the work the code you serve them does is collect and present data to the server.
Like, they get to see the code they run, but there's no insight to the code you run to deliver whatever service you're doing. Maybe this is obvious to other people lol, I just hadn't thought of it till now.
Yes, this is the reason AGPL was created. With AGPL software you have to open your changes, even if you don't distribute it and only use it serverside. There are still nuances, but this is the main gist.
This is known as "Tivoisation" (after a dead set top box company), and is the driving motivation behind GPLv3 and some other licenses adding terms to cover this.
Like, they get to see the code they run, but there's no insight to the code you run to deliver whatever service you're doing. Maybe this is obvious to other people lol, I just hadn't thought of it till now.