It's strictly in-game, it seems. In Galaxy, when I click on the My Progress button, it shows:
Achievements N/A.
When you hover over it, there's a tooltip that reads, "This game does not have achievement support".
I think if you want cheevos, your best bet is probably to buy it direct from Spiderweb. They say they'll give you a plain download and include a Steam key. So you get the best of both worlds.
http://www.spiderwebsoftware.com/geneforge/