So it seems, but there are other factors. What if Windows was opened, would that be a hit? Certainly not, it is just way too complex and bloated and requires a strict chain of command and large coherent teams to operate. I remember Watcom C/C++. It was opened and just withered away even though it arguably was the best compiler at the time.

Symbian could have worked as open source if they started 10 years earlier and branched out a separate open source real-time kernel in addition to a separate application kernel. The mixed approach of the EKA2 never really worked in real life. The "real" OS in all phones is the real-time OS, and a open source upstream kernel similar to the Linux kernel could possibly work, maybe.

Symbian is still the best OS for mobile devices by far, but increasing HW specs shrinks the practical real benefit in relative terms. It is all in the hands of Nokia now, and I hope they stick to it.