Some features require activation (details here).

How is this implemented, since it's ostensibly open-source?

implementation

Boot a working system up, go to the shell, and look in /root/kerbynet.cgi/scripts/. Grep for 'checkfeature'. The /bin/checkfeature is what validates the keys, and it's a compiled binary.

workarounds

There is a checkfeature patcher mod available.

At its heart is this bit of code:

#!/bin/sh
rm /bin/checkfeature
echo "#!/bin/sh
mkdir -p /Database/var/register/system/\$1
" >/bin/checkfeature
chmod 755 /bin/checkfeature