The Cal3D User's Guide is licensed under the GNU Free Documentation License (GFDL).
The Cal3D library is licensed under the GNU Lesser General Public License (LGPL). which among other things, allows you to link proprietary applications with it. The Cal3D team strongly believes in the Free Software movement and provides this library without any additional restrictions. However, to make this a "fair deal" and to support the future development of the library, we invite you to follow these points when using the Cal3D library in your project:
Seriously consider releasing your project under a free license too.
Read and understand the LGPL and make sure that your usage of Cal3D complies with it.
Include a prominent mention about the usage of the Cal3D library in your project.
Send a short message to us when you release your work.
Provide feedback to the Cal3D project to help us enhance it.
Furthermore, here are a few other possibilities to help the Cal3D project:
We are always in need of models, animations, textures and demos. So, if you have something to spare, send it along!
Sponsoring and donations can definitively help the project, just contact us.
Have you heard of a new animation technology? Is there a freshly written, earth-shaking paper about inverse-kinematics on your desk? Fell free to send such stuff to the Cal3D project, so we can put it into the library!