An eprom card can hold eproms instead of rom chips it's being used before they went into production to create some cheap carts.
For development a Flash-cartridge (Flash-rom) is easier but these EPROM cards are much cheaper only you need to clear the eproms and burn them again before using them so it will take sometime and will slowdown development.
The best thing to use is BJL just load your program with a cable into the Jaguar ram this is nice for testing. When your product is almost complete you can think about eprom cards...