Add info about the OpenID logo usage license.
Fixes #15
diff --git a/LICENSE b/LICENSE
index 562f7eb..444bc67 100644
--- a/LICENSE
+++ b/LICENSE
@@ -29,3 +29,10 @@
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+---------------
+
+OpenID® is a trademark (registered in numerous countries) of the OpenID Foundation.
+
+The OpenID logo in docs/_static/flask-openid.png is used under the
+OpenID trademark and service mark license, as defined on http://openid.net/trademark-license/.
