You can root an iPhone and do it too. If I install Ubuntu, I know I have full open source. I can do anything. Not so with an Android from your carrier.
Which you can replace (and I would love to know about those legal threats against developers of alternative UIs - I've not seen it)...
Which have already been bypassed, because the OS is open source so the developers can see how to get around it with new versions...
The same gets done with the iPhone, thus my point: You have to root/jailbreak either to get your freedom.
one example
Sorry, that's not what you think it is... Read the comments of the link you provided and you'll find out that HTC was sending a cease-and-desist for hosting HTC code, NOT for changing or rooting the phone. HTC doesn't care if you change the home screen, just that you cannot post their ROM code for their own UI on your site. BIG difference there.
The same gets done with the iPhone, thus my point: You have to root/jailbreak either to get your freedom.
No you don't. You can install alternative home screens on an Android phone without rooting. You cannot do that on an iPhone. Simple as that.