But that doesn't seem to be the case, as Apple hasn't monetized Xcode and the iOS SDK libraries differently since the DMA came up.
Apple can charge for the SDK and all that it entails, but they can't charge for apps getting to run on users' iOS copies, as that's not something IP law contemplates.
What happens when a fully FOSS iOS dev environment comes out, like the way you can compile Windows binaries on Linux right now? What would Apple be charging for then?
The CTF offsets Apple's costs in developing and maintaining the "core technology": the OS and the frameworks that the developer uses in their application.
The CTF is it's own refutation. A competitive market should not need to kiss anyone's ring in order to function.
At least on AIX and other UNIXes, the system compiler and GCC worked together. HP-UX was a special kind of hell.
A sibling reply pointed out that developer kits and distribution deals for consoles (which are general purpose computers, regardless of how they are presented, as much as modern smartphones are) are extremely expensive (and there are no alternatives for distribution).
The point that I am making is that the idea that you can develop and distribute for free on any platform is a relatively new one.
But regardless, it seems like a good idea in general, and proven to work, so why shouldn't we want more of it? I don't see the problem with applying the same logic to game consoles etc - that racket also needs to go down.
Those who are surprised that you have to pay for access to an ABI have obviously never had to pay for their compilers from their software vendors (the price for the HP-UX garbage compiler was eye wateringly high).