> and use it on their device

To use the modified software on your device you have to be a "App Developer" (or whatever Apple calls it), and in the process to becoming one accept the TOS imposed by Apple. So you are only as free to run the modified source as Apple wants you too be.

You don’t need to enroll in the developer program to run code on your own device anymore, only if you want to distribute through the App Store.

You have to refresh it every week or something though, right? At least last time I tried it (two years ago maybe?), the self signed apps needed to be re-signed after a short period of time. Fine for development and testing, not so great for actual real use.

Huh, TIL. Last time I tried was ~2 years ago.

I think the problem is that they need to provide a way for you to sign your own binary such that it will work on the hardware?

Which is entirely possible, no?

It's possible, but they have to actually do it.

But they do? Xcode does this.

I'm not sure if requiring you to buy a Mac meets the requirement. (I don't mean this sarcastically, I really don't know if it does).

You do not need Xcode or a Mac to sign applications.

Ok, so let's assume I was able to build the source and sign it without needing a Mac. Am I then able to run my newly signed program on my iPhone freely? Do I need to get it into the app store? Are there limitations to installing it directly to my phone?

Just trying to figure out where the incompatibility will the GPL is coming from.

GPL v3 very clearly requires it. "Corresponding Source conveyed under this section must be accompanied by the Installation Information".

I don't see how what you've quoted requires this?