Yeah, basically it means that the chain of trust is (without a computer) broken all the way down in userland (booted iOS), and limera1n only acts as an injection vector for something that gets loaded on iOS boot to modify the loaded kernel in memory and allow unsigned code execution. An untethered bootrom exploit is one that ignores the signature on the LLB (such as Pwnage 2.0 or 24kpwn) allowing us to upload a modified LLB and iBoot (such as one that loads a jailbroken kernel, or in our case, OpeniBoot).