Pacrom reads GXE files, but doesn't read ones encrypted wrongly (just try encoding a freelauncher with a different PDUID than your own and see what happens if you run it in Pacrom). Ergo, it has GXE compatibility, NOT a GXE --> FXE converter. Ther former is a very useful thing that I urge all programmers to put into their bioses; the latter is a byword for warez.
That said, they may use the same bits of code as it were. Just one's for a very good purpose, the other isn't...