Custom maps for the Tacops 3.0 maptool need to be in a .bmp file format. You can load in a existing .gif map file with common software like MS PhotoEditor+ or PaintShop Pro, make some edits, save it as a .bmp format and then load it into the maptool.
.bmp is a good standard to use for the Windows environment - just about every software graphics package can read this format. I'm not sure why the maps shipped with the product are in .gif format - maybe Mac/Windows compatibility?
I don't believe that there should be any legal implications of editing the .gif maps of Tacops 3.0 but perhaps MH might comment.