Due to the European General Data Protection Regulation, Tunngle shut down on 30/04/2018.
REF:
https://www.reddit.com/r/Games/comme...042018_due_to/
Looks like Game Ranger is still an active alternative.
Supports:
Delta Force
Delta Force 2
Delta Force: Land Warrior
Delta Force: Task Force Dagger
Delta Force: Black Hawk Down
Delta Force: Black Hawk Down: Team Sabre
PS
Free Lan looks like an open source tool worth investigating