Cannot access beta (HumbleBundle, Windows)

That's normal, yes. Humble bundle users don't get access to the beta.

It's normal but I don't know if it's intended.

I believe you can get access to the beta by purchasing the game through steam?

Ennui said:

I cannot buy it, Steam Store says (rightly so) it is in my Library. Humblebundle gave me a Steam code which I used, and I only got Retail version. Midiman even let me try to add a spare SG code he had, and Steam said I already owned this item and could not add it. So I guess I am stuck without a beta.

I guess being more specific, if you purchase SG fresh again on an account that doesn't have SG, you should unlock the beta.
You can link the two accounts to share the game library between the two, which gives your regular account access to playing the beta.

Look into Steam Family Sharing if you're interested.

I've done it with other people cross country to let them try some games in my library before they purchase them to see if they like them / it will run on their computer.