Heh, that's mine and about my Sciter project.

Sciter is pretty full implementation of HTML5 and CSS, has scripting engine on board, etc. So, indeed, I am personally competing with teams behind WebKit, Trident, Gecko, V8 (JS Engine), Chakra (MS JS Engine) and bunch of others.

And recently with ReactJS (Sciter got Reactor - native implementation of ReactJs), Angular and others.

And that is really a fun project to work on - many different paradigms on the same code base.