osgART version 2.0 and above is released under the OpenSceneGraph Public License (OSGPL). As stated on the openscenegraph website:
The OpenSceneGraph Public License is based on the Lesser GNU Public License (LGPL) and includes the wxWidgets additions to LGPL which provide a clear statement that distribution with proprietary applications is accepted.
In short, the license cover application built with static libraries (as for example widely used for Android programming).
Note: As osgART is based on a plugins architecture, if you release any software produced by osgART please be aware of the license for each plugin.
Commercial osgART 1.1
You can purchase licenses for osgART 1.1 from ARToolworks.