Apple does not have to open up the whole system - there are some good reasons for limiting the access of applications to the system part of the filesystem and the bare hardware.<p>However, Apple also very much limits the ability to run e.g. Squeak as an app on IOS, you might run it, but not download source code over the internet. And if you read the Anandtech iPad Pro test you can see how much software is held back by the  restrictions on exchanging data between apps.<p>I am writing this as an Apple user and owner of several IOS devices. IOS was a huge accomplishment in touch UI usability, now it is time to develop the computing part to similar levels.