They would still be stored on your Palm. The only difference between the SD card version and the download version is that the SD card version's registration system is keyed to the SD card's serial number instead of the Palm's HotSync Username - in all other respects they're identical, they can both read fixed data files from an SD card or from internal memory and they both store flashcards and custom dictionary entries in internal memory.
The SD version is really just a marketing idea, a way of reaching out to customers who might be uneasy with the idea of installing downloadable software - if you've already gotten PlecoDict installed and working on your Palm then there's no benefit to using the SD card version.