From the looks of the comments, as well as the frequent references to "written, but unread" memory, this appears to be a dump of the US release. The original JP release was for the Famicom disk system, which had more sophisticated music playback, as well as a three save slot support (similar to Legend of Zelda) instead of passwords. These bits of vestigial code/memory likely still exist in "dummied out" form in this US based source.

IMO, Legend of Zelda source would probably look similar. But by that time, Nintendo of America started support for battery based save states, so someone more experienced in NES hardware might want to compare and contrast the two codes bases to see how much Disk System code was salvageable for battery based backup purposes.