The LIGAND program package is available with manual at no charge
from Dr. P.J. Munson at NIH, Bldg. 10, Room 6C101, Bethesda, MD
20892, USA. You have to specify which version (IBM-PC, DEC, VAX
or Macintosh) you need, and have to sign a licence agreement.
They normally do not distribute the source code. I do not know
about any source on the Internet.
Hope this helps.
Dr. Tibor Szentendrei, (szentendrei at usuhs.usuhs.mil)