The font is derived from the Kedage font developed at IISc. Kedage is a good typeface, yet the font is largely unusable because of incomplete Opentype tables. Vagisha borrows the glyph set from Kedage; some glyphs have been newly created. The Opentype tables have been entirely newly created.
Additionally, Vagisha supports Vedic symbols required for Taittiriya shakha. Details are available in the IME manual and font document.
Vagisha borrows Basic-Latin block (0x00-0x7f) glyphs from the Charis SIL font.
Vagisha is usable with all Opentype-aware applications like notepad, wordpad, MS office, SSOffice, Libreoffice, Openoffice, IE, Firefox, and Chrome.
VagishaGr implements the same features as Vagisha using Graphite "smart font" technology instead of Microsoft's Opentype tables. In addition, there is also support for Samaveda svara markings (not available in Vagisha).
VagishaGr is usable with Graphite-aware applications like Libreoffice and Openoffice.
Vagisha and VagishaGr are totally identical/compatible, except for the Samaveda svara-s.
MS Windows did not support positioning of Taittiriya svara-s on non-Unicode Scripts till ver 8.1. Ver 8.1 does. The font has both proprietary and Unicode svara-s for use on Windows Ver < 8.1 and >=8.1 resp. BhashaIME automatically recognizes the ver of OS and uses the appropriate.
Both the fonts have been used to render the entire samhita and padapatha texts of Taittiriya-samhita.