Is there a reason we get the Battlecry games but not the main series? I loved the heck out of Warlords I, II and III, but I sadly never got the play IV. I'd love to see it on GoG.

I think the reason is that Steve Fawkner has not rights for selling Warlords IV. Ubisoft should has it. And it's much harder to make agreement with Ubi than with Steve... :)

If you can find an old box, it should be less than $10.
I don't know if UPLay drm is needed (not in old boxes):
http://www.ubi.com/US/Games/Info.aspx?pId=113
Official devs game page:
http://www.infinite-interactive.com/games/warlords-4/
Last patches:
http://www.warlorders.com/warlords4/downloads
(I here did the French translation of some last patch)

You can try on some old games site too... (I didn't try)

On my Win-7-32 system "compatibility with XP" mode runs fine.

Warlords III: Darklords Rising was the peak of the franchise (though some Warlords II fans will disagree with this and say W2 was the best.) and if you enjoyed that game or any of the previous Warlords games you won't likely find much to like about Warlords IV. It does have it's good points such as using a more robust character system similar to the Battlecry games (only turn based) but it lacks the customization and options that W3: DLR had. There are only a few hero classes and several units per side/faction/race and no means to add more or alter the ones that exist. Combat is largely the same as previous Warlords games except Steve added some unnecessary Heroes of Might and Magic -style presentation (without the HoMM tactical options and control.) which is to be expected since they could not get away with old 2D graphics in this day and age. I don't remember if there were randomized maps (I am pretty sure there were though).

On the plus side KGB (a Warlords fan from way back) has been making patches to improve the game over the last several years, but there is only so much anyone can do with the system being the way it is.

It works now, thanks for the tip!

It would be nice to have Warlords III: DLR as well or instead. There is a Warlords game on iOS, but we can't get the real ones I guess. :(

The problem here is that the source code of 1.02 version of W3 DLR (or whatever number it is, I don't remember correctly) is LOST, and the only .exe Steve and the team have is 1.00. So they said there's no reason to make a unthankful work to patch it again when there are only a couple of hundred people around the world interested in this work. And living in Australia is not the cheepest variant of living, so the "money issue " is very important.
So, it's likely impossible probability to have Warlords 3 here on GOG. And Warlords 4 as well, I guess. Alas, but the new gaming industry reality is harsh and unforgiveable. Money is the main matter, 'cause everyone wants to eat and to feed one's children.

It's simply run for me on Win 7 64 bit, if I add Patch 1.5!

I agree with the above comment. Warlords III DLR was the best of the series. I have the game installed on all my Laptops with Win XP. You can still buy it pretty cheap on ebay, or buy it on Amazon. FYI, the Game CD for Warlords III DLR does not have copy protection. I have made a copy for myself so I won't wear out the original CD. In my opinion, it is one of the best turn-based Fantasy games besides HOMM III, & Age of wonders. Everyone interested in this genre should give it a try.