Firefox OS is not bootstrapped off of Android. In fact, it is nothing to do with Android. Firefox OS is a Gecko engine (the one behind Firefox) being run by a light-weight Linux kernel. There is no Android in there.
Err, well, no. You're both right. The lowest levels of B2G are the kernel from Android, RIL (telephony stack from Android), and other little bits like that (e.g. gralloc, which is what allows the fast texture sharing). There's a lot of Android in B2G, but it's well out of the view of users.
