I was looking the repository https://github.com/ladislav-zezula/StormLib and it's using the MIT license, so far so good.

However, looking at the following file https://github.com/ladislav-zezula/StormLib/blob/master/src/pklib/explode.c

static char Copyright[] = "PKWARE Data Compression Library for Win32\r\n"
"Copyright 1989-1995 PKWARE Inc.  All Rights Reserved\r\n"
"Patent No. 5,051,745\r\n"
"PKWARE Data Compression Library Reg. U.S. Pat. and Tm. Off.\r\n"
"Version 1.11\r\n";

It seems to be using a compression algorithm that is patented. It probably was obtained using reverse engineering techniques.

Can I use StormLib? Can I use PKLib? Neither?

Apparently the term for patents is 20 years, so I'm good?

1 Answer 1


Per Wikipedia:

The .ZIP file format was released into the public domain in 1989.

So the patent side may be OK, but there may be a bigger problem:

PKWARE Data Compression Library for Win32 is as far a I know a proprietary commercial product.

So I would contact the author of Stormlib for clarification

  • To be clear, I never mentioned the .ZIP file format. Doesn't the patent only prevents other people (like StormLib) from using/selling the same idea in USA for 20 years? after that, any person/company can develop the same product and use it/sell it in the USA.
    – Gam
    Jun 18, 2017 at 12:34
  • @Phantom indeed, but the patent is about deflate en.wikipedia.org/wiki/DEFLATE hence my confusion... I am not a patent specialist. There could very well be other subsequent patents granted around the same topic. The 90's were wild in this respect. And even if in this case 20 would apply, 20 years have not passed... and the bigger issue is one of copyright not patents e.g. the likely reuse of "PKWARE Data Compression Library for Win32" which is not open source... Jun 19, 2017 at 13:59
  • The patent for DEFLATE was fileld on Aug 21, 1990, 2017 - 1990 = 27 years xD. Why copyright matters here? the Stormlib guy wrote it from scratch, he didnt "steal" and copy it from PKWare. Even if he reverse-enginered it, there's no way to prove that. He could be a smart guy that read the specification and simply wrote the code.
    – Gam
    Jun 19, 2017 at 14:07
  • 3
    You wrote: "the Stormlib guy wrote it from scratch" ... the copyright notice seems to state clearly that this code comes from PKWARE. So short of any other clues I would take it as face value. The resolution would likely require some serious historical digging, contacting authors and getting a copy of the original PKWARE SDK. Jun 20, 2017 at 8:34

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