This is actually the original base game! It was made as a kickstarter. It's the real thing. It's not the full game (which you can buy on steam).
This is free early prototype/demo of commercial game Raft. The full game is currently in Early Access on Steam:
https://store.steampowered.com/app/648800/Raft/
Raft never had kickstarter or other crowd funding campaign. It was originally a school/hobby project by 3 Swedish university students during their final year in the university in 2016 - 2017. It became so popular that the three decided to turn it into a commercial game after graduation.
https://raft-game.com/presskit.html
Plenty of people have copied the concept since, especially on mobile, but this is the original prototype that started it all.