It is possible to generate a custom PRINCE.EXE with CusPop.
Another tool to create customizations is PrinHackEd.
You may need/want to pack or unpack the file.
Use diffpop to find out what changes were made to PRINCE.EXE files.
Use PR to export and import resources (.bmp, .pal, .wav, .mid) from and to .DAT files.
Convert GIMP gpl palettes to JASC pal palettes with gpl2jascpal.
PRM (Princed Resource Manager) is an old wrapper (GUI) for PR.
There is a PoP1 to PoP2 level converter.
.SAV and .HOF
There are several SAV and HOF file editors.
The drawmap utility can create simplified maps from PoP1 and PoP2 level files.
TPC adds a cheat menu to the Mac version of PoP1.
The Total Packs and poplaun provide user-friendly interfaces for tweaking and playing custom levels.
PoP1 Studio contains a database/library of PoP1 game resources.
See also the various old tools.
SNES Password Analyser