> Yes you can compile and install your own software, but AFAIK, you have to pay a yearly fee for the privilege of doing so.

While this was true in the past, this hasn't been the case for a while if you want to build and run on your own personal device. There are some minor caveats, but if you want to compile and run an app locally on your device you don't need to pay Apple the $99 any more.

The idea that the version of Android that most people actually use is "open" is arguably a myth - when you look at what the "closed" parts of Android now include, it's a large amount of the feature set that actually matters to most ordinary consumers, and is often the "stick" Google uses to get OEM partners to follow the overarching vision for the platform.