Many of the universal rusEFI boards are open source hardware.
As of Jan of 2022 rusEFI LLC is experimenting with vehicle-specific boards being proprietary, not open source hardware. while Hellen One framework is open source, only Hellen 121 VAG and Helen 154 Hyundai are open source. For the majority of Hellen vehicle specific boards we only publish complete schematics while not publishing gerbers and BOMs.
TL,DR: it' not that complicated:
Wire-in boards: open
PnP: mostly not