It's not another JS template engine - it's a pure JS implementation of Mustache that's apparently significantly faster than Mustache.js.

They also support compiling of templates for deployment purposes, which is nice.

And then twitter released one! Awesome timing! Now you don't need to write your own.

yeah we felt the same way, but we're trying to move off of mustache.js for performance reasons (also for size in our new tweet embeds projects).