Hi there, lead dev of UL here (we didn't post the link, HN just found our beta :)).
That top-level repo is just our packager/samples, 90% of our code is open-source and available on GitHub (released under LGPL), see our WebCore [1] and AppCore [2] modules.
The product as a whole contains two proprietary modules which are indeed non-free but allow free use in non-commercial and commercial projects up to $100K in gross revenue.