Versions 0.1, 0.2, 0.3, 0.4 and so on are public releases. They can be obtained here or on itch.io.
We get about one intermediate update between public releases here, but it seems entirely up to the developers' whim. Perhaps only for versions they feel need additional testing.
Edit: oh, and you can read developers' logs here:
You must be registered to see the links
Edit 2: Speaking of developers' logs, logs for 0.3.5 sound very nice. Especially the parts about research and groups being campaign-wide. And catgirls. I love catgirls.