Yeah it's analogous to the patch listed on their support site for the DLC:
https://store.gearboxsoftware.com/support/
Namely this file:
http://updates.gearboxsoftware.com/dlc/Borderlands_Worldwide_Update_PC1.1.0.zip
The ini file in that directory from the Steam forums post definitely references SecuROM though
I'm hoping it doesn't install it until the DLC is installed (as it prompts for a license key according to the posts).
EDIT: I'm guessing the retail patch doesn't contain any of the SecuROM stuff since that's already installed via the normal game installation?
EDIT EDIT: There's also this post on NeoGAF:
http://forums.beyondunreal.com/showthread.php?t=190244 Which confirms what I found and notes the presence of SecuROM on some level in the game's .exe file.
*crosses fingers* Pretty please let it just be someone being stupid. I really like this game and want to support it but this just reeks of ineptitude either at Gearbox or 2K. AFAIK, Valve just takes whatever the developer or publisher give them and blast it out without any questioning. I'm just sitting here hoping that someone sent the wrong build out.
EDIT x3: Brizz, is you qualm the existence of SecuROM in general, or is it because they're unnecessarily applying it to DLC (and possibly retroactively applying it to the main game)? I don't see any griping about SecuROM in the Arkham Asylum review and the Steam version of that also contains the DRM. Just confused on your stance here.
EDIT x4: So in the retail patch there's ShippingPCWillowGame.exe. My guess is that this is the SecuROM retail version of the game executable and was probably accidentally pushed out via the Steam auto-update. Or something like that, since I am noticing about a 4 MB discrepancy in file size between what is in the 1.10 retail patch and what is currently in my Steam directory.
Again, ineptitude not malicousness at work here I feel. But we'll see how this pans out.