Do they have DRM?

Short of the usual Steam API jazz, no (they even have proper LAN). The reasoning has to be either a 2K stubbornness or a high asking price for the license.

Any new development on this? I'm really hopeful Civ5 will be available for purchase on GoG one day. No hope for Civ6,but 5 would do the trick.

So far no news. The only thing we know is that the game was discovered on gog's database but that was about 4+ years ago I believe. Maybe now that 2k decided to remove their launcher from their games, we might have a bigger chance for it to come here.

I just found out you can pirate steam-exclusive games without requiring steam client, so I will keep doing that until these games show up on gog, then I will buy them here :).