Is ditroff public domain?

[David Brown]

  I'm running 4.3+NFS from U of Wisconsin.  I'm interested in the differences
  between ditroff and troff, and probably the sources to ditroff and dtbl, if
  they are public domain.

  Thanks in advance,

    David Brown

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David Brown
Armstrong State College, Savannah, Georgia
uucp: ...!{akgua,allegra,amd,hplabs,ihnp4,seismo,ut-ngp}!gatech!gitpyr!david
ARPA: david at pyr.gatech.edu