Is design of this site open source?

or not? front page etc…

I don’t think the current landing-page theme by Eduardo Santos is, at least I cannot find it in the Grav GitHub repos (https://github.com/getgrav). However, other parts of the front like http://learn.getgrav.org is available there.

Nope, the getgrav.org site is not open source. We do have over 30 themes freely available though! http://getgrav.org/downloads/themes