The latest itch.io version does play without having a Steam account. However it hasn't got the Cerulean Vale map (yet). As a beta-tester however, I have the distinct feeling that some (small) beta bugs - some of those I even signalled - are back in the game, I fear that Mothership used one of the older beta versions to compile the itch.io version.
Viewing post in The full Aven Colony release is now live on itch.io!
Nope, the itch.io version is from the very latest version of the game.
The Cerulean Vale map is Steam-only at this point. We'd like to add it to itch.io as well when we're able to do so, but currently, since 99.9% of our customers are playing it on Steam, we can't justify it.
Sorry to hear this is still requiring Steam for you. I'll have our engineering team take a look.