Apple has a somewhat similar tool called iAd Producer.https://developer.apple.com/iad/iadproducer/ (I believe you might need the free developer account to view the page, however.) I know you can create iBooks Author widgets and other HTML5 components that aren't necessarily ads. Even if Google's goal is the same as Apple's (i.e. creating advertisements), I think that Google's branding makes their tool a bit more interesting for someone not expressly interested in creating ads.