According to the HTML5 spec for the script tag, it’s totally fine to use <script> with a type attribute set to any valid MIME type. That includes MIME types like text/html or text/plain.
According to the HTML4 spec for the script tag, it’s not quite fine:
“There are two types of scripts authors may attach to an HTML
document: Those that are executed one time when the document is loaded
[and t]hose that are executed every time a specific event occurs”
You don’t need backbone for templating. You can use e.g. jQuery or my personal favorite, Mustache.js.