In case of Obelisk has ASIC chips inside, the hashing core chip did not change, an the ´knife´at the end is only a software wrapper change on the controlling board, that could be ported to Bitmain controller boards also... I´m thingking as a simple of an ID or serial number check, or changeing the number of blake2b rounds before the result is sent to the pool.
The chips in the Obelisk were designed with a backup algorithm from day one, the changes are not simply in software. Since the Obelisk shipped after nearly all other ASICs, it is extremely unlikely any other vendor has support for the algorithm changes.