As stated on game page, Itch.io version will no longer be updated and all developers efforts are going toward commercial release on Steam aimed to happen next year:
"Raft will release on Steam Early Access in 2018 with multiplayer, reefs and much more new content and features! To be notified when it launches, please visit our Steam page and press 'Add to your wishlist'! We are not releasing any new updates on Itch.io as we are working towards a Steam Early Access release. To read more about this announcement, visit our Blog!"
Also from Raft FAQ on Steam page:
“Will Raft release on Mac and/or Linux?”
We are first and foremost focusing on Windows. We would like to support more platforms in the future but due to certain parts of the game making porting more difficult we cannot at this time give any promises.