KaiOS is a closed source fork of Firefox OS that is embedded with a lot of ads API.
As a low-end mobile phone system for poor people, however, it is definitely not a good/ethical system.
Why Firefox doesn’t re-initiate its Firefox OS project for those USD20 smart feature phones?
Why a open source Firefox decided to help a closed source fork to upgrade B2G engine?
An open source system can motivate more developers to join and develop apps for poor people.
And the web apps developed for KaiOS can be simply transferred and adapted to new Firefox OS.