"Will have Free friend pass: Invite a friend to join your adventure for free with the Friend’s Pass. As long as one of you owns LEGO Voyagers, you can both play the full co-op experience together."

"games is possible to play with one copy of the game if playing local or streaming. Both Use our Words 1 and 2"

"Friend pass with full cross play after the new update."

"Now has friend pass, coop story and speedrun. https://store.steampowered.com/app/2477230/Timemelters__Friend_Pass/"

"Will have friend pass for the full game. From the creators of "It takes two" and "A way out""

"Has friend pass, fun party game where you have to find the real players among NPCs"

"Owners of the full game can invite friends who have the demo to play the full game for free!"

""5-10 (!) local presidential advisors and their mobile devices can help him get re-elected in this social deduction party game." Only one copy of the game needed. Currently free 2 play."

"If you own Paper Pirates, you can create a lobby and any of your friends can join even if they don’t own the game! Share the room code and they can join from a web browser on their own PC, laptop, mob"

"From steam page: In Whispers in the West, your friends don't need to buy the game to join a room. As long as the host owns the case, anyone invited can join for free using the Steam demo +3 friends"