I wouldn't be surprised if the original source code is probably lost and forgotten in a ZIP drive stored in a basement somewhere in Tokyo.
I've made a similar point in an earlier comment, but consider the following:
Even if the original sources leaked in a human-readable format, the original game was probably written in a mixture of the device-specific dialect of the Mips R3000 assembly used by the Nintendo 64, whatever in-house assembler macro routines SGI provided for the RSP game-specific microcode, and some C89 glue code in an IDE like Metrowerks Codewarrior 4, by a team of overworked japanese developers in a hurry.
We can safely assume that the final decompiled code is way more readable/usable than the original.
I've made a similar point in an earlier comment, but consider the following:
Even if the original sources leaked in a human-readable format, the original game was probably written in a mixture of the device-specific dialect of the Mips R3000 assembly used by the Nintendo 64, whatever in-house assembler macro routines SGI provided for the RSP game-specific microcode, and some C89 glue code in an IDE like Metrowerks Codewarrior 4, by a team of overworked japanese developers in a hurry.
We can safely assume that the final decompiled code is way more readable/usable than the original.