Hey bud, if you want to download this game just go to this link ► https://raft.itch.io/raft
To download for free, just click the download button, when prompted with "name your own price" just click the "No thanks, just take me to the downloads" link above the donation interface.
But, if you do have the money to support the developers I do suggest donating money as this game has really great potential and the more you can support them, the efficiency of content as well as updates for the game will increase!