Subject: Re: Licensing constraints...?????
To: David Maxwell <>
From: Don Lewis <>
List: current-users
Date: 08/29/1997 00:17:43
On Aug 28,  9:23pm, David Maxwell wrote:
} Subject: Re: Licensing constraints...?????
} > 
} > True. I think that's why CTM'd need some sort of promise from the user to
} > actually use the diffs. Like you get a copy of the source for the day when
} Encrypt the diffs using a checksum of the file the diff is to be applied
} against. Or, have the protocol use a checksum of the file to be diff'd to
} request the diff in the first place.

What protocol?  In FreeBSD-land the CTM diff files are just mailed out
periodically to whoever subscribes to the list.

That said, the CTM files aren't you're normal context diffs.  They're closer
to ed scripts that say to delete lines 502 through 507 and substitute these
seven new ones.  As a safety measure the program that applies these patches
it checks the md5 checksum of the file before applying the patch and doesn't
apply the patch if the checksum isn't correct (I think it might also verify
the checksum after applying the patch).  This pretty much means that you
would need to start with a copy of the file with the correct copyright
notice.  You can override the checksum sanity check, but if the line numbers
are off at all, you'll end up with a mangled file, unlike what happens if
you apply a context diff.

If everything in the file besides the copyright changed, you could extract
the code from the CTM file without having a copy of the copyright, but
that's also true of a context diff.

If someone other than the copyright holder makes a one line change to
the code and distributes the patch in CTM format which doesn't contain
any of the copyright holder's code, should the copyright on the original
file be attached?  It's common practice for context diffs of these types
of changes to be distributed without copies of the copyright notice,
even though the context diff contains both the original line of code as
well as a number of lines of context, all of which fall under the copyright.

Hmn, maybe the solution is to tag the proper copyright notice on to the
end of each line.  That way the notice would be attached to context diffs
and everyone can take credit for each line of code they write or modify.
You'd need to require everyone to make printouts on really wide paper,
though, so the notices aren't cut off.  Otherwise we need to modify diff
to attach the proper notices  ;-)

			---  Truck