TAL was developed internally within the BBC as a way of vastly simplifying TV application development whilst increasing the reach of BBC TV applications such as iPlayer. Today all of the BBC's HTML-based TV applications are built using TAL.
There are hundreds of different devices in the marketplace and they all use slightly different technologies to achieve the same result. The purpose of TAL is to allow you to write an application once, and be confident that it can be deployed to all HTML-based TV devices.
We also have a sample application that you can use as a guide to help you build your own applications.
For developers who want to modify and contribute to TAL, we have a page on testing which you should follow before starting development.