The Pinboard theme is in the WordPress theme repository and released under the GPL license, this means that you are free to use and redistribute the theme code.
The GPL license gives you….
- the freedom to use the software for any purpose,
- the freedom to change the software to suit your needs,
- the freedom to share the software with your friends and neighbors,
and the freedom to share the changes you make.
More here: http://www.gnu.org/licenses/quick-guide-gplv3.html