who writes the code for wireguard module

[FredFresh]

Probably a stupid question, but I am looking for confirmation who is writing the code of the wireguard module used inside the opnsense.

Thank you

[Patrick M. Hausen]

The UI and tooling, so the "OPNsense module"? The OPNsense team, i.e. Deciso in the Netherlands, and potentially volunteers.
Or do you refer to the kernel implementation? The FreeBSD project. Refer to the source code for the list of contributors:

https://cgit.freebsd.org/src/tree/sys/dev/wg/if_wg.c