KleskBY did a GPL compatible implementation of Steam API for Zircon:
https://github.com/KleskBY/Steam-SDK-Bridge-for-DarkPlaces
Pictured: me and KleskBY taking the Steam Integration for a test drive. I hosted the server and due to Steam Networking, did not need to port forward.
As Zircon Beta is a fork of DarkPlaces Beta, as you can imagine the code changes are quite compatible with DarkPlaces Beta.
https://www.moddb.com/mods/zircon-engine/news/zirconsteam-integration
KleskBY did a GPL compatible implementation of Steam API for Zircon:
https://github.com/KleskBY/Steam-SDK-Bridge-for-DarkPlaces
Pictured: me and KleskBY taking the Steam Integration for a test drive. I hosted the server and due to Steam Networking, did not need to port forward.
As Zircon Beta is a fork of DarkPlaces Beta, as you can imagine the code changes are quite compatible with DarkPlaces Beta.
https://www.moddb.com/mods/zircon-engine/news/zirconsteam-integration