Unless we see the agrements on both sides it is just speculation on our part. And why should they do this?
Anyway, since we can only speculate her is my 2p worth.
Company 1 is not interested in desktop OS's.
So it licenses this avenue to company2 to get some cash.
Company2 says, hold on if we cant own it outright can we get the sole exclusivity to the desktop market and since you (company1) are not developing the OS for desktops, can we modernise the desktop software.
Company1 says OKAY go ahead, however, we want you to feedback any changes you make to us as part of the license. Oh and in no way can you add restrictions (eg desktop software) that would affect us selling it to new owners in the future. IE If the new owners want to use it for a desktop then I'm afraid we can sell it to them and they can buy it for that reason.
Company3 (who has an interst in the OS for desktops) says. Hey company1, we can use the Old OS on our desktops, but it would save us a lot of time and cash if we could buy your "newer" version of the OS. OH PS it is a condition of the sale that we can use it for desktops (we have heard that company2 has an exclusive right to that)
Company1 says... its okay company3, we have a clause in our contract that says we can do this.
Company2 and 3 enter a few years of arguments.
Insert company names where you want... Is that about right?