What programming language and database technology does Tally ERP use for development?
Tally ERP is built with a programming language developed specifically for Tally called TDL (Tally Definition Language), a high-level object-oriented language.
Since the language is proprietary, I think you'll have a hard time finding much public information on the language outside of Tally-specific courses or paying for access as a developer.
You can view Tally's Help section on their website here.