I don't think I can properly say how cheap this looks to me.
HTML mixed with code in the same file? A new language? A new database? What makes an app written in opa better than a PHP codebase where HTML is mixed with PHP all over?
This opa project doesn't look like such a big deal to me. It just limits freedom too much from what I can see.
Build something like this which merges the HTML with some weird looking code and you've wasted quite some time for nothing.
Wt has been around for a while with an approach not far from this one and I never stopped thinking it's one major piece of junk.
To the guy who posted this link for SEO purposes:
I'll make sure to block that site from my browsers, it's 100% trash.
Buzzword bingo aside, the idea is interesting. That said, mixing html and code is not my idea of fun debugging... Is that the way you do it on big apps as well, or is it done that way to make the chat example as small as possible?