I'll preface this by being fair and saying that the iTunes store does officially list the app for iPad 2 / OS 5.1 and above. But it does run on an iPad 1. Kind of. I have to force-quit every other app before BG will launch. It will run great for about 10 to 15 minutes, then crash. It almost always crashes when playing a cinematic. There are also lots of little fiddly bugs, like sometimes clicks don't register, characters start walking in a random direction on game load, etc.
I'm surprised it was approved by Apple at all, and I would strongly suggest anyone thinking of trying it on the iPad 1 to skip it and play on another platform (when available!). The engine must be pretty clunky. I know the iPad 1 is limited on resources, but considering an iPad 1 can run high-end audio applications and lots of other games with much higher graphic quality, I'm surprised that the small amount going on in BG at any given time causes such a resource load.
YMMV
I'm surprised it was approved by Apple at all, and I would strongly suggest anyone thinking of trying it on the iPad 1 to skip it and play on another platform (when available!). The engine must be pretty clunky. I know the iPad 1 is limited on resources, but considering an iPad 1 can run high-end audio applications and lots of other games with much higher graphic quality, I'm surprised that the small amount going on in BG at any given time causes such a resource load.
YMMV