Nudi was developed by the Kannada Ganaka Parishat and became the keyboard layout and software widely used for Kannada, including by the Government of Karnataka. The legacy Nudi fonts are ASCII fonts: Kannada is typed on an English keyboard and drawn by the font, so the file contains English letters.
Later Nudi releases moved to Unicode, and the Unicode Nudi keyboard layout is still how many people type Kannada today. What remains are decades of documents typed in the older ASCII fonts.
Baraha, a separate Kannada typing package, also produced ASCII text in a closely related layout. This converter reads the layout the two share, so documents from either usually convert with the same mapping, but it does not claim support for every version of every font.