RainTPL 3 is been officially released and is been published on Packagist, so you'll be able to download it from github or install in your application with Composer (the suggested way).
We also started to work on the documentation available as wiki on github, https://github.com/rainphp/raintpl3/wiki, so now you'll be able to contribute to the code and the documentation as well.
You can download RainTPL 3 from github:
Or with Composer with the following require:
For any feedback and questions you can write here: