Android is so widespread due its nature as the QNX of the mobile world. A manufacturer gets it for free and then can add shit on to it.

The vast majority of users chose a cheap smartphone, not Android explicitly. Samsung and others do not even mention Android anymore, that for specsheets like the processor being used. China has this large number of Android devices which are non-Google, no Play Store, no Google Now, nothing.

Now Jolla comes in and acts as an alternative to Android. For whom? End users? 99% don't give a shit. Like asking which fuel injection systems your car uses.

So what does Jolla offer to manufacturers to choose it over Android? Even less restrictions than the open Android? Less cost? If so, it can't be price - will they adapt the OS for specific hardware for free as well?

Android compatibility. You want a KILLER feature? iOS compatibility. Enable devs to simply copy over their code and run their shit on Jolla.