ImageMagick has a habit of reversing the color palette of 1-bit (black and white) images from one version to another, and UnForm's interpretation can be the inverse of what is expected. If your version of Magick has this issue, you can change the Magick command line configuration for 1-bit images to reverse the image it outputs.
To do this, edit uf90d.ini and look for the bmp1 setting. The color inversion is controlled by the presence or absence of the -negate option. Just add it or remove it:
bmp1="%i" -compress None -density %dx%d -units PixelsPerInch -filter Box -resize %xx%y -rotate %r -type BiLevel "BMP3:%o" >/dev/null 2>&1
bmp1="%i" -compress None -density %dx%d -units PixelsPerInch -filter Box -resize %xx%y -rotate %r -type BiLevel -negate "BMP3:%o" >/dev/null 2>&1