On Steam Monolith has been renamed to "Star of Providence", updated and the DLC has been included into the main game.

So, on GOG we get none of that? Kinda feel shafted.

I was wondering the same thing, hopefully they won't abandon the GOG version.

I just checked Steam and Star of Providence is a Team 17 pixel graphics shooter, not Monolith.

I didn't understand the point of this answer to be honest.
This is the discussion section related to the game Monolith, a rogue-like pixel shmup.
This game has been RENAMED to Star of Providence on Steam (which was previously called Monolith) and soon they will update the game with new content.
But here on GoG it is still called Monolith, which means the devs haven't updated the game yet on GoG.
Hope this clarifies any doubt.