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From: robjung@world.std.com (Robert K Jung)
Newsgroups: comp.compression
Subject: ARJ and patents
Message-ID: <1991Apr25.004117.20744@world.std.com>
Date: 25 Apr 91 00:41:17 GMT
Organization: The World Public Access UNIX, Brookline, MA
Lines: 27


In reference to a posting concerning avoiding ARJ like the plague, let
me clarify the patent issue.   The ARJ 2.00 compression mechanism has 
been designed to be compatible with a myriad of LZ77 sliding window 
compressors.  Therefore, it is entirely possible to build an archiver
completely compatible with the ARJ format without coming within MILES
of the ARJ 2.00 mechanism.  In fact, that is what ARJ 1.10 is.  ARJ 1.10
uses the public domain compressor in AR002.  And it is completely 
compatible with ARJ archives.  

There is NOTHING in UNARJ that is proprietary to me.  It is just a
good decompressor.  Unlike UNIX COMPRESS which uses a patented compressor
and a patented decompressor, the UNARJ decompressor is not patentable as
far as I can tell.  The patentable mechanism in LZ77 mechanisms
usually involves the string searching mechanism.  This mechanism usually
does not affect the decompression operation.

ARJ 2.00 is just a slightly faster way to do LZ77 windows. 

And I make no special claims to the ARJ archive format.

I hope that the fact that you can build ARJ compatible archivers with
public domain algorithms eases people's concerns about using the ARJ 
format.

Sincerely,
Robert K Jung  (robjung@world.std.com)