Isn't the firmware in the flashcard that is used? The sgminer code may also be in that since it would be impractical to embed permanently into a rom, don't you think? Anyone have any experience with this?
By the time you get your miner the firmware is flashed to the microcontroller. You can still obtain it, but it is as useful as the compiled sgminer. You can only edit it with a Hex editor, but development is not possible without the source code.