OK after a bit of research I think I know a way to get it on the PS3. First you have to convert the file to .psu format or use xport or Max Drive to get the data onto an official PS2 8MB Memory Card. Then once that is done, using the PS2 memory card converter for the PS3, you just have to transfer the data so that the adapter converts it from .psu format to .psv format. Once that's done, you can easily transfer and backup the file via USB drive. Just copy it onto a flash drive and when you want to give it to others with a PS3, there is no conversion needed, just send them the data and they can put it onto the PS3 via flash drive.

I myself can't do it since I can't transfer the .psu files to my memoy cards, but if someone CAN do this, I suggest you convert the files so you'll have two sets. One for PS2 users that have X-port, Max Drive, etc. and one for PS3 users.