How do I contact admins?

Best bet is probably a support ticket: https://support.gog.com/hc/en-us/requests/new?form=other&product=gog

However, what issue are you having exactly? Maybe I can point you in the right direction. Thanks.

Correct. The developer/publisher is responsible for generating the game update (by uploading it to galaxy or by sending it to GOG). GOG is responsible for creating the offline installer from the game update. It depends. Sometimes the developer/publisher can't be too bothered because of the small number of GOG customers compared to steam (a.k.a. "second class customers"). Sometime GOG can't be too bothered because they care more about galaxy than they do about offline installers (a.k.a. "third class customers").

Honestly, if having your games up to date is important to you, then perhaps GOG is not the store for you. Yes, in many cases. But GOG doesn't really seem to care enough to chase after delinquent devs, nor to warn customers that they will be buying an abandoned or outdated product (even when they know it full well).

Specifically about Against the Storm, it looks like GOG's fault, not the dev's.

GOG has last updated the offline installer to the October 31st update (version 0.36.13R). Since then the dev has released three new updates on galaxy (November 3, 10 and 11), which have not yet been reflected in the offline installer. The last two could be explained as very recent, but the November 3 update is already eight days old.

InDev games with numerous updates over a short period of time (like this game seems to be) are really not a good fit for GOG, unless you use galaxy.

Thanks for all the replies, much appreciated.
Against the Storm has been resolved after inquiring numerous times on Steam per the 'dev'.
I understand that GOG is not quick to update many of the titles they offer, still a fan however.