Despite the poorly chosen name, this is a WYSIWYG tool for animation, not a site design tool. If all you care about is markup, use a text editor and make your animations by hand. Compared with Adobe Edge Animate (which is very similar), the markup is actually very clean (aside from the big script block, which is for ad functionality and also animation / drawing routines). You can see the animations defined as real keyframes in CSS, not overly reliant on javascript, which is good. It means there is a chance of taking those and using them independently of the JS runtime code, and also that execution will take advantage of native browser animation functions, rather than being bottlenecked by JS code.

It would be nice if there was some options for stripping out the Ad specific javascript. But even at ~55k this is a pretty slimmed down codebase considering what it does. Swiffy, which converts flash files to HTML/javascript has a 200k JS runtime.

A tool that designers can use to make animations in HTML5/CSS3 is desperately needed if we are ever going to move to a truly post-Flash world. We can't expect everyone to be an HTML developer, and achieving the same level of complexity and polish is extremely difficult when just working with code.