What's also important: all earlier co-op and funding from AuroraOS many years back (of Russia) has been cut off by Jolla.

Sailfish OS is NOT 100% closed source, as some still claim it to be. Jolla has also promised that the REMAINING blobs will be opened. There are good reasons for this situation.

95% of Sailfish OS bases on free / open source software. The OS itself utilize Linux kernel (which is open source). Mer that was used is open-source. Qt Framework API's base on open-source Qt API's.