Its source code is distributed under the terms of GNU General Public License, version 3.0. You are allowed to use, modify or study it completely for free.
The icon was created by Nadja (Artcore), thanks for licensing it as CC.
selfoss is named by the wonderful waterfall in Iceland (see Wikipedia). Many single waterfalls converge to produce one big fall. This seems to be a good metaphor for the many sources from the web which will be shown in one stream.
FancyBox on the front page is from fancyapps.com.