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November 1998

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1998.11.11 23:20 "Re: lzw decompression.", by Daniel Mccoy
1998.11.17 16:50 "Re: lzw decompression.", by Larry Jones
1998.11.18 13:50 "Re: lzw decompression.", by James Palo

1998.11.11 23:20 "Re: lzw decompression.", by Daniel Mccoy

Jim Palo wrote:
>Note that you cannot use LZW compression without a valid license from UNISY. 
>They have patent on the technology and are aggressively enforcing it. I am not
>lawyer but SGI is probably liable for providing this in the TIFFLIB.

I'm sure SGI sends all the money people pay for libtiff right to UNISYS.

Seriously, I'm not a lawyer either, but I believe UNISYS is only
claiming royalties for commercial use.
There is no problem with SGI providing libtiff since it is freeware.
If you grab libtiff and include it into a commercial package
with lzw support, then you should probably be talking to UNISYS's 
lawyers about sending them royalties.
If you use libtiff/lzw for educational or research purposes, 
I don't think they ask for any money.
I don't know offhand what they want commercial users to pay, but if they 
make it too expensive it gives people too much incentive to create an
alternative, so they usually try to keep the royalty below most people's
pain threshold.

Also, all this is a big reason that the inflate/deflate stuff from ziplib
got added to libtiff.  This is an alternate compression scheme
that provides essentially the same functionality as LZW without being
encumbered by patents.
Now if Adobe would just roll that into the TIFF spec we could all kiss
UNISYS's lawyers goodbye.

Dan McCoy