OK, this should work on Linux (only tested it on a Mac so far, but it does build with both Clang and GCC, so it should be fine). Basically, build it using the makefile. You'll get a binary called convert_save. You need both the original ROM file (it pulls information it needs out of the header), and...

I have a (very) rough conversion program, which might work. I've attached a converted Phantasy Star 4 save file. I'll put the converter up somewhere as well, when I get a chance to compile a Windows version of it.

(BlackAura here, author of GP/DC - Don't have my main account password on me at the moment, so...) The .gps file should be the save file. It's named with an 8-digit hex code (the ROM's checksum). From what I remember, the save files are compressed using Deflate, and there's a Dreamcast VMU header an...