Please
tmorgan:
I was provided the bootloader hex files and custom boards.txt file and told to unzip it to Documents/Arduino/hardware/.
Is that all that was in the zip file? It would be helpful is you would attach it to a message here(click the "Reply" or "Preview" button and an "Attachments and other options" link appears).
This boards.txt is not correctly formatted for installation in Documents/Arduino/hardware/. It looks like either the person who wrote it never bothered to do even minimal testing or else it was intended to be pasted into the Arduino AVR Boards package. You could do that but I don't recommend it because you will need to redo it over again everytime you install a new Arduino AVR Boards/Arduino IDE version.
Without the full package I can't do complete testing but I think if you change your boards.txt to this it should work:
fhp.name=HoloProjector I2C FHP (Blue)
fhp.upload.tool=arduino:avrdude
fhp.upload.protocol=arduino:arduino
fhp.upload.maximum_size=32256
fhp.upload.maximum_data_size=2048
fhp.upload.speed=115200
fhp.bootloader.tool=arduino:avrdude
fhp.bootloader.low_fuses=0xFF
fhp.bootloader.high_fuses=0xDE
fhp.bootloader.extended_fuses=0x05
fhp.bootloader.file=holoprojector/hp_i2c_fhp.hex
fhp.bootloader.unlock_bits=0x3F
fhp.bootloader.lock_bits=0x0F
fhp.build.mcu=atmega328p
fhp.build.f_cpu=16000000L
fhp.build.core=arduino:arduino
fhp.build.variant=arduino:standard
Adding the arduino: before the components that are not included in the HoloProjector package tells the Arduino IDE to get these from the arduino core instead. Those missing components were the reason for the error you were getting.