Jolla could be the true third (or fourth) ecosystem by using Open Source to the full extent. Include a slightly curated collection of open source repositories to get their phone full of content. I.e. it should be free to signup and they should just make sure there is a semi-respectable community behind the repo (with access cut if turns to piratism, child porn, etc). The only chance of success they have IMO is to get the best of FOSS software (and content) ported to them. They will never attract developers as an "Android alternative without users".