The whole point of open source is sharing development cost in exchange of shared IP... Why on earth would you open your code, but not work with others?
"Since starting the company about a year ago, Mr. Hurmola said Jolla has been working hard to make its Sailfish operating system capable of working on different types of devices, including smartphones, touch-screen tablets and televisions. Another benefit with the MeeGo-based software is that it won't require the same high-end and costly hardware needed to run the latest versions of Android or Windows Phone."
Jolla Sailfish is benefiting from an infusion of 200 million Euros. I expect it will soon be a viable option to Google & Apple devices, and that it's just a question of time before it surpasses them. Establishing the Hong Kong Headquarters is a brilliant move.
All the code is open and aside from the kernel under BSD, so the Chinese OEMs can crank all the Android tablets & phones they want, without paying Google & releasing their changes (as they seem to mostly ignore the GPL requirements for kernell changes anyway).
If you want to get the whole experience - Google apps & Google play, you have join the Open Handset Alliance and play by Googles rules.
The end result is the same though - more Android compatible devices, with Google as the default search engine, support for showing ads in applications and using Googles services. And all this with closed development cycle & open code.