With the current license I think it's fine for you to add modified sources to your stuff (i guess it says you should add notes in your source that it is, but since it's closed source who can check )

Just wanted to clarify that it's not really a "Do whatever with it", even if it's close

    1. The origin of this software must not be misrepresented; you must not
    claim that you wrote the original software. If you use this software
    in a product, an acknowledgment in the product documentation would be
    appreciated but is not required.

    2. Altered source versions must be plainly marked as such, and must not be
    misrepresented as being the original software.

    3. This notice may not be removed or altered from any source
    distribution.

http://ardorlabs.trac.cvsdude.com/Ardor3Dv1/browser/trunk/LICENSE

feel free to add some ardor3d notes/mentionings on the jpct site