Kinda unfortunate announcement timing, very close to recent conflict in certain place I shall not name where a lot of children died. I hope the story is worth it or it's just another Limbo clone.

It looks like the page for this upcoming game has been removed from the store.

A quote from Steam: "Hinweis: Auf Anfrage des Publishers steht Torn Away auf Steam nicht mehr zum Verkauf."

Translation: "Note: At the publisher's request, Torn Away is no longer for sale on Steam."

So, this has nothing to do with GOG.

Thanks, I hadn't noticed that message, I wonder why the developers decided to abandon the project, it looked very promising.

Doesn't look like the developer abandoned the project, but the project having lost its publisher.
If you investigate a bit further you could imagine why the (bilateral?) decision was made to part ways (perelesoq being a Russian developer, and the now former publisher Nordcurrent hailing from Lithuania), at least for the time being.

It's out on Steam with a different publisher now. I wish it would come to GOG too. Wishlist.

According to the developers, the game was rejected by GOG because it was produced in Russia:
https://www.reddit.com/r/pcgaming/comments/1bh3be2/we_made_a_story_driven_game_that_players_loved/kvc2ml6/