Shareware. Does this mean in order to unlock more content, I should go and buy the game on steam?
Yeah, shareware means that it is a free version of the game with locked or restricted content, rather than a set up demo. You can also buy the game on here for a bit cheaper if you wish and get a Steam key for the game with your purchase here.
We also have a summer sale here on Itch that starts the 24th and are a part of the summer sale on Steam whenever that starts if you wanted to wait a few days for it to be cheaper.