Great. In what area you want to help? If it is the front-end, simply clone the repository and browse the www/templates/ directory in order to get some idea about the current state of the project.
How to install the engine - you will probably need a working local instance of the engine. The article is about installing on VPS, but the same directions can be used for local web server as well.
The template engine specification - the basis of the front-end is the template engine. Here is more or less full description of the syntax.
The contributions model - here is described how to make changes and submit them to the project.
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