I was just looking at Tumblr's page on how to create custom themes: http://www.tumblr.com/docs/en/custom_themes#pro_tips
And I noticed that they are using JS that is similar to Knockout or even Backbone am I right?
Lots of templating languages use this notation, or something similar, so I'd say, maybe, but probably not.
Smarty springs to mind as something that uses a similar notation.
And though it's not identical, Jinja also makes use of { and }.