NoxTM: Somebody actually asked the question on the Steam forums not so long ago; the dev member didn't sound confident. The fact they'd release the base game on GOG when they weren't fully confident they'd then follow up with extra content doesn't sit easily with me, and seems more like something larger, greedier companies would do.
Wow, that sounds like someone is just being too lazy to put in the extra effort to bring it here. Why did I buy this on day one, oh I know; just so I could have my trust and support thrown to the hounds for choosing to give it to a small company.