I'm not aware of anybody reproducing the exact softdevice design, but there are open source BLE stacks out there that run on the nRF528xx family, for example:

I'm not aware of anybody reproducing the exact softdevice design, but there are open source BLE stacks out there that run on the nRF528xx family, for example: https://github.com/apache/mynewt-nimble https://github.com/apache/mynewt-nimble