"A radical, uncompromising, plug and play personal server, offering one-click installation and simple configuration of open source software services that run over Tor V3. The Embassy is your sovereign territory in the land of the Internet. No technical expertise required."
Found on the Fairphone forum.

Up to 4 CM4 modules with lots of interfaces, found on
https://www.raspberrypi.org/blog/raspberry-pi-compute-module-4/

Source and binaries for (among others) 64 bit Windows can be found on https://github.com/debauchee/barrier/

Wiki about the Slice media Player. Last updated 2015-11.

Brief description of a failed attempt to install the virtual AGC
from https://www.ibiblio.org/apollo/ on a Raspberry π 4 running Raspian.

EISL was written by Kenichi Sasagawa
https://qiita.com/sym_num/items/793adfe118514668e5b0
The license appears to be similar to BSD/MIT to my non-laywer eyes: https://github.com/sasagawa888/eisl/blob/master/license.txt
It provides an interface to WiringPi, allowing control of the GPIO pins on a Raspberry π.

How to install FreeBSD/ARM on computers of the Raspberry Pi family.

Collection of articles describing various applications for the Raspberry π (in german).

The entire desire to do this came about from reading about building a Stratum 1 clock using a Raspberry PI at http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html and from the use of a Sony radio clock to provide WWVB pulses from the WWVB receiver module that was used in the radio clock.

However, all of the projects and examples I found used Linux which I did not really want to use. I much preferred to use NetBSD, but it lacked a number of critical features that would be required to make a properly working Stratum 1 clock. Interrupt support for the GPIO pins was needed and adding a PPSAPI driver that could be triggered by a GPIO interrupt would be necessary.