Help a developer - do you have this DLC?

I have released a mod that unfortunately turned out to have a bug that made the 9 G&K-specific civs unplayable, so I want to fix this as quickly as possible. I have a fix that depends on whether a player has the free "Upgrade 1" DLC installed, so I need to know how widespread this DLC really is.

Unfortunately it doesn't show up in the in-game DLC list, so here's how to check if you have the Upgrade 1 DLC:

1. Find the DLC install folder on your computer. Some typical locations:
   
   PC with Steam: C:\Steam\SteamApps\common\Sid Meier's Civilization V\Assets\DLC
   PC with Steam (alt): C:\Program Files (x86)\Steam\SteamApps\common\Sid Meier's Civilization V\Assets\DLC
   PC without Steam: C:\Program Files (x86)\Games\Civilization 5\Assets\DLC
   MAC: See this post!
   
   
2. Look in the subfolders for a file called Upgrade1.Civ5Pkg, probably in a folder called Shared. If you have the file, you have the Upgrade 1 DLC.
   
   
3. Answer the poll - choose the first option from the top that applies to you. If you are familiar with the Upgrade 1 DLC, please also answer the question in the first post below!
   

(I was going to post this to the C&C forum, but decided I would get less selection bias if I posted it here to a more general audience. Hope that's OK!)

Bonus question: the Upgrade 1 DLC seems to add Cow, Pearls and Stone resources, Stone Quarry and Trading Post improvements, some region-specific Forest and Jungle textures, and other miscellaneous stuff.

Does this mean that Upgrade 1 is redundant for users of BNW - can I disable Upgrade 1 safely in my BNW mod without affecting gameplay?

I wouldn't. I've had everything to do with civ 5 on the day each dlc/expansion came out; I noticed that the upgrade1.Civ5pkg most recently updated on 15/10/13, months after I had BNW. I would suspect if it were deleted, it would be restored next time you went onto Steam.

Thanks, it's useful knowing that there's been an update to this DLC since BNW. The mod won't actually delete anything, it would just block the Upgrade 1 DLC while the mod is being used. I strongly suspect it's OK to do this in a BNW mod, but I'd like independent confirmation from an experienced modder.

Everyone should have Upgrade 1 dlc.
It was added to base game after release of Spain and Inca DLC.