Edit in JSFiddle

/*restore the previous refernce to Backbone before the last version of Backbone.js was loaded*/
var lastBackboneParsed = Backbone.noConflict();

//verify the Backbone in the global scope points to previous version
console.log(Backbone["I'm the previous owner of Backbone in the global scope"]); //logs true

/*verify Backbone.js is contained in the new lastBackboneParsed namespace and not Backbone namespace*/
console.log(lastBackboneParsed.VERSION) //logs 1.0.0