[comp.sys.atari.st] Copyright questions

cs4e3ao@maccs.UUCP (cs4e3ao) (12/27/86)

I recently downloaded a file called IBMSRCE.ARC from a local BBS, it
turned out that this archive contained most of the source files 
for ARC (IBM version 4.??)

What I would like to know is ...

  Are these files in the public domain? (they all contain copyright
    notices in them)
  If they are PD then could someone please send me the ST sources 
    (vers. 5.12 I believe)
  If they are not PD then what could/would happen if I were to produce 
    and market a program which was in some way compatible with ARC
    files? (say my program were able to extract files from an archive)
    Would things be different if the program I wrote was PD?

Any help would be appreciated as I do not want to start this project until
these questions are cleared up.

Thanks 
  Grant Henderson