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From: blochowi@rt9.cs.wisc.edu (Jason Blochowiak)
Newsgroups: comp.sys.apple
Subject: ShrinkIt Compression (modified LZW) and legal issues
Summary: Apparently someone does own this...
Keywords: Compression, legal issues, LZW, ShrinkIt
Message-ID: <3980@puff.cs.wisc.edu>
Date: 7 Dec 89 20:54:41 GMT
Sender: news@puff.cs.wisc.edu
Reply-To: blochowi@rt9.cs.wisc.edu (Jason Blochowiak)
Organization: U of Wisconsin CS Dept
Lines: 54
References:


	This is reprinted without permission from Doctor Dobb's Journal #158
(December 1989), from the letters section:
--
	Dear DDJ,
	"LZW Data Compression," by Mark Nelson (DDJ, October 1989) is a nice
exposition on the LZW algorithm. But before your readers decide to use this
method in any application (except perhaps for purely personal use), they should
know that the algorithm is patented.
	Terry Welch is listed as the inventor of U.S. Patent 4,558,302, "High
Speed Data Compression and Decompression Apparatus and Method," December 1985,
assigned to Sperry Corporation (now Unisys). The Unix compress utility and
several commercial and shareware programs are apparently infringing on this
patent (unless they have licensed it from Unisys).
	If you wish use this method in a commercial setting, you should contact
Unisys for a license, or at least consult your legal counsel first.

	Ray Gardner
	Englewood, Colorado

Mark responds: When I wrote the LZW article I was unaware of any patent on the
algorithm. The issue has just surfaced in the press because of concern in CCITT
group 7 over approval of the BTLZ algorithm for data compression in the V.42bis
modem standard. Unisys, British Telecom, and IBM apparently all have some claim
on the algorithm. Robert Bramson, a patent attorney for Unisys, has been quoted
as saying they will license the algorithm for a one-time fee of $20,000.
	I have not seen the Unisys patent, so I don't know what their specific
claims are. However, I am not aware of any attempt by Unisys to show
infringement by software developers. The BTLZ algorithm seems to be
concerned with hardware implementations. In the event that they do pursue their
claim with software developers, they will be very busy, as there are literally
hundreds of potentially infringing programs in the commercial marketplace
alone. And they certainly cannot claim a comprehensive patent of basic LZ
compression, as Terry Welch, the patent holder, was not the inventor.
	I agree with Mr. Gardner that anyone who intends to use LZW compression
in a commercial product would be wise to consult legal counsel first.
	Finally, I would like to suggest that DDJ reads begin a letter-writing
campaign directed to members of Congress, the ACM, and the IEEE. The current
confusion over copyright and patent issues in the software development world
only serves to stifle both creativity and productivity. At present the only way
questions regarding the validity of copyrights and patents are being answered
is through random decisions from legal proceedings. Copyright and patent laws
both need to be updated to work properly in the 1990s.
--

	Somewhat interesting, eh? Perhaps it's better that Andy didn't go
commercial with ShrinkIt/GS ;)

	Btw, DDJ (whom I have no affiliation with, blah, blah, ...) does tend
to have some interesting articles, even though it's IBM oriented.

--
      Jason Blochowiak - blochowi@garfield.cs.wisc.edu or jason@madnix.uucp
       "Education, like neurosis, begins at home." - Milton R. Sapirstein