It's the same "324" op-amp. TI uses an "LM" prefix whereas NEC uses "uPC" to identify its parts.
Attached are the datasheets. Note that the schematic diagrams are identical save a current source of 4uA in the TI diagram which has a value of 6uA in the NEC version.
I bet the uPC324 was the chip the author found on his board when reverse engineering it, but they wrote "LM324" next to all of the op-amps to indicate than any 324 op-amp would work.