J3D reader copied from [http://code.j3d.org/] (http://code.j3d.org/download.html). The java code is licensed with GNU LGPL. The Matlab/Octave code I have added is released to the public domain.
I have not changed any of the java code apart from making two C3DHeader fields public. I have deleted the classes that were not needed for reading a .c3d file.
Look into build.xml and compile.bat for building with ant.
I use this to call org.j3d.loaders.c3d.C3DParser from Matlab to parse c3d motion and analog data files created with a VICON motion capture system. I tested with c3d files created with VICON version 2.1.1 motion capture software (test.m), and on a few sample files from. The former worked, the latter produced garbage. Your mileage may vary.