Bloopist allows users to embed javascript in their blog posts. Normally, it isn't safe to allow users to upload arbitrary JavaScript. Malicious users could upload JavaScript that steals login information from other users.
Bloopist prevents anything bad from happening by using Google Caja. Caja is a service that cleans up JavaScript and makes it safe for anyone.
If you want to use jQuery in your Bloopist posts, you should use the versions that Google hosts:
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.9.1/jquery-ui.min.js"></script>
Luckily, Google hosts a lot of different versions of jQuery (2.1.4, 2.1.3, 2.1.1, 2.1.0, 2.0.3, 2.0.2, 2.0.1, 2.0.0, 1.11.3, 1.11.2, 1.11.1, 1.11.0, 1.10.2, 1.10.1, 1.10.0, 1.9.1, 1.9.0, 1.8.3, 1.8.2, 1.8.1, 1.8.0, 1.7.2, 1.7.1, 1.7.0, 1.6.4, 1.6.3, 1.6.2, 1.6.1, 1.6.0, 1.5.2, 1.5.1, 1.5.0, 1.4.4, 1.4.3, 1.4.2, 1.4.1, 1.4.0, 1.3.2, 1.3.1, 1.3.0, 1.2.6, and 1.2.3 as of 11/19/2015).
Some other Google Hosted Libraries are AngularJS, Angular Material, Dojo, Ext Core, jQuery, jQuery Mobile, jQuery UI, MooTools, Prototype, script.aculo.us, SPF, SWFObject, three.js, and Web Font Loader!