Its out on steam, and was wondering if it was going to be only for steam.

I would wish for the days when GOG gave answers in the forum - it were rare back then.
But today GOG is not even able to answer support tickets.

But yes, this question should be answered by GOG ...
It is really strange to offer the 1st part and than not the 2nd.
That's just not correct!

At least we should get an info on the release day of Act 2 ...

Added (10. March 2021):
It was really announced four hours ago (and ~3.5 month after release) that it is now available on GOG:
* https://www.gog.com/news/release_hiveswap_act_2
and 'Hiveswap: Act 2' it refers to "forum/hiveswap_act_1" ... GOG ... ;)