i copy paste the interesting comments of coderus and szopin:
coderus:
You know, Jolla team itself is not responsible for opensourcing decisions, it's all about investors.
And about Nemomobile, check Asteroid smartwatch project, it's all done by Nemo community. And because it's not a commercial organization (Yet?).

szopin:
Coders probably did not see this as a venture that would bring them ROI (bashers are usually not coders, armchair CEOs), some got tired of Nokia and never getting there, others probably just went android, as there is at least a possibility of some income there, however slim chance it might be. Open source relies on fanboys in a way and android killed proper linux I'm afraid, people would be angry about things like this: https://talk.maemo.org/showpost.php?...36&postcount=9 not anymore, it's business as usual in the new linux world nowadays, android is king


thanks to both for ever useful opinions