This is a tool used to generate game fonts from system fonts.
Usage: 
- Open wswFont, select "Tools->Add Warsow charset".
- Select your font, size, ect.
- Select "File->Export font".
- Put the 2 files generated by the export (.wfd and .tga files) inside "Warsow/basewsw/fonts/".

The .fnt files are archives from the generator tool. They are saves of the settings used to generate that font, so it can be done again. Those are not used by the game and are not part of the game font.