You can download the software and related fonts for free from these official and verified platforms:
In the corridors of Tamil Nadu’s Secretariat and the bustling classrooms of government schools, a quiet revolution has been taking place. It isn't powered by high-end hardware, but by a crucial piece of software that allows millions to type in their mother tongue. tn govt keyboard interface software free download
The Tamil Nadu government has been actively promoting the use of Tamil language in government offices and institutions. To facilitate this, various software solutions have been developed to enable the use of Tamil language on computers. One such software is the keyboard interface software, which allows users to type in Tamil using a standard keyboard. You can download the software and related fonts