A wordpress theme used for http://blog.openstreetmap.org, the main OpenStreetMap blog run by the foundation, and also on https://join.osmfoundation.org (different wordpress instance)
It's lightly customised version of the "twentywelve" theme: http://wordpress.org/themes/twentytwelve
Harry customised it try to make it vaguely similar (same font at least) to the main OpenStreetMap site, e.g. the 'diary' pages at: http://www.openstreetmap.org/diary Not exactly the same, particulary as the main site now no longer has a sidebar for diary entries.