In a 2014 article for ZDNet, Senior Technology Editor Jason Perlow said that, with consumer iPad growth tapping out, Apple needs to do the "unthinkable" to push into a line of business applications and vertical markets. The "unthinkable" is licensing iOS.
However, this will never happen. Perlow says that, for Apple to grow tablet share, it has to expand into additional markets. And the largest market of opportunity is enterprise line of business applications and verticals. He may be right in that regard, but Apple will NEVER license iOS under CEO Tim Cook's leadership. That's a lesson he learned from his mentor, Steve Jobs.
In 1997, after returning to Apple, Jobs killed the Mac clone program implemented by former CEO Gil Amelio. The program was intended to expand the market penetration of the Mac. From 1995 through mid-1997 companies such as Power Computing, Motorola, Radius, DayStar, and UMAX made desktops running Mac OS X (no Mac laptop clone ever saw the light of day).
However, there was no evidence that the clone program expanded the Mac market. Mac clones only seemed to cannibalize Mac sales. In 1997, Jobs ceased negotiations of upcoming licensing deals with OS licensees. Since the clone makers’ licenses were valid only for Mac OS 7, Apple’s release of Mac OS 8 left the clone manufacturers without the ability to ship a current Mac OS version and effectively killed the cloning program.
At the time Jobs didn’t want to license Apple’s “crown jewels.” I'm 100% convinced that CEO Tim Cook feels the same way about licensing iOS.