Hello all. This is Kevin Kiley As promised... Below is a cut from the second conversation I had with Dr. Mark Adler ( co-author of ZLIB ) this weekend regarding some of the possible legal 'patent' issues that have been raised ( Ryan, Dirk, others? ) as they might relate to using ZLIB inside of Apache to dynamically compress the presentation layer content ( E.g. IETF Content-Encoding ). The 'summary' of what Mark had to say ( full text below ) is that he has no idea if using ZLIB as the main engine for dynamic data compression will violate generic 'lurker' patents or not. Even Jean-loup did not specifically address these kinds of patents with regards to ZLIB. Dirk told Ryan he has some specific patent 'numbers' that he is concerned about but he won't be back online until Tuesday so still not sure which ones Dirk was referring to or if they are relevant. Our own research in this area turned up a number of these generic 'dynamic compression of content' style patents, one of which is... US5652878 - Method and apparatus for compressing data. Issued to IBM on July 29, 1997 ( Filing date: Oct 2, 1995 ). We had lots of highly paid attorneys looking for these things and rendering opinions but, unfortunately, it wouldn't do any good for me to post our findings because ( as is the case with most IP legal work ) the opinions are not 'transferrable' in a legal sense. The 'gist' of it is that they are probably not worth worrying about since they are simply 'method' patents and the 'general use' clause always kicks in in these cases if/when there is a challenge. There is also the 'public good' clause. We've been compressing Apache presentation layer content all over the world for over a year now and we have not received any 'legal' complaints from anyone but the currently distributed mod_gzip does NOT contain or use ZLIB at all so whether that matters or not... I do not know. I imagine it does NOT since the 'lurker' patents are mostly of the generic 'method' type. If the ASF really needs to be 'severe clear' on this I'm afraid there is no substitute for having your own IP attorneys give you their own green light ( in writing ). Here is all that Dr. Mark Adler had to say about the 'generic' presentation layer data delivery patent(s)... >> At 8:45 PM EST - Saturday 9/8/01, Kevin Kiley and >> Dr. Mark Adler had the following conversation... [snip] >> Kevin Kiley asked... >> >>The Apache group doesn't appear to have any problem with >>the compatibility of the ZLIB/LIBPNG license with their >>own ( more restrictive ) ASF License but a few of the >>'patents' of ( mild ) concern at Apache are those that are >>floating around out there which are as generic as they can >>be and basically ( supposedly ) cover the delivery of any >>compressed presentation layer data via any communications >>interface. ( In other words.. all of IETF Content-Encoding ). >> >>Ring any bells with you? > > Mark Adler wrote... > >No. But patents are sneaky things, and I haven't spent any time >looking for the lurkers out there. Jean-loup spent quite a bit of >time reading patents to make sure that the zlib deflate >implementation did not violate any (and there were some that we had >to skirt, where for example the level 1 compression in zlib could be >faster were it not for a patent). But he did not look for >compression delivery patents. > >mark [snip] Yours... Kevin Kiley PS: As with the previous message regarding ZLIB memory leaks, Dr. Mark Adler's verbatim comments are reprinted here on this public forum with his full permission.