Two words:
Export. License.
This is *not* easy to get. I've heard some absolutely nightmarish stories from International Launch Services, and they're as "inside the game" as you can get (coming from Lockheed Martin).
Whether this is due to covetous NASA interference, or genuinely home-grown idiocy at the State Department, launching these modules on a foreign rocket could be VERY problematic for Bigelow.