sdk/lib/3rdparty/adns/GPL-vs-LGPL

   1               GPL vs LGPL, in the context of adns
   2               -----------------------------------
   3
   4 Several people have asked me to release GNU adns under the GNU Lesser
   5 General Public Licence (LGPL, formerly the Library GPL) instead of the
   6 `stronger' GPL.  This file is intended to answer most of these
   7 questions.  If you still have questions or comments, please mail me at
   8 <adns-maint@chiark.greenend.org.uk>.
   9
  10 Typically there are two or three kinds of situation where people make
  11 this request: the first is where someone is developing a proprietary
  12 program and wishes to make use of adns but doesn't wish to make their
  13 program free software.  The second case is where a free software
  14 project is currently using an MIT-like licence or the LGPL and fear
  15 `GPL infection'.  The third case, which often overlaps with the
  16 second, is where another free software project currently using a
  17 GPL-incompatible licence, wishes to use adns.
  18
  19
  20 1. Proprietary applications of adns
  21 -----------------------------------
  22
  23 So, let me get this straight.  You're writing a proprietary
  24 program, by which I mean that you will not be distributing source code
  25 and not allowing users to modify and share your software; most likely
  26 you are doing this for your own (personal or corporate) financial
  27 gain.
  28
  29 However, you want to take advantage of adns, software which I have
  30 spent my time and effort on, and which I release as free software so
  31 that everyone can improve, share and use it.
  32
  33 Don't you think that is a little hypocritical ?  I'm sorry, but I
  34 don't want you to just take my nice convenient software, without
  35 giving something back to the free software community or giving the
  36 same rights to your users as I do to you.
  37
  38 If you really aren't the nasty kind of person I've described here, for
  39 example if you have a good reason other than your own selfishness for
  40 wanting to restrict distribution of your program, then perhaps you
  41 should contact me to discuss it.
  42
  43
  44 2. GPL-avoiding projects (MIT licence, et al)
  45 ---------------------------------------------
  46
  47 Some free software projects prefer to avoid the GPL and other licences
  48 which force the software always to be free.  Instead they use
  49 something like the MIT X licence, which allows proprietary versions of
  50 their software, or the in the case of some free libraries, the LGPL,
  51 which allows proprietary applications.  I have to say that I think
  52 these people are misguided, but that doesn't mean that they don't have
  53 a perfect right to do that.
  54
  55 Some of these people think that merely writing to an interface
  56 provided by GPL'd software will cause their program to become GPL'd
  57 too, even if they don't distribute the GPL'd software.  I don't think
  58 this is the case.  I'm perfectly happy for non-GPL'd but
  59 GPL-compatible software to refer to adns in its source code.  However,
  60 I think that exectuables (or compiled libraries) which contain or are
  61 dynamically linked against adns must be GPL'd; likewise executable
  62 programs (whether compiled or in an interpreted language) which
  63 require utilities from adns to function properly must be GPL'd.
  64
  65 So, you can distribute your non-GPL'd program source which needs adns
  66 to compile (provided it's under a GPL-compatible licence), but people
  67 who wish to distribute binaries must do so under the terms of the GNU
  68 GPL.  This may make sense for some GPL-avoiding free software
  69 projects; people can still make proprietary programs from your code,
  70 provided that they make some provision to replace adns with something
  71 whose copyright allows proprietary versions.
  72
  73 However, this doesn't make much sense for the authors of LGPL'd
  74 libraries.  All I can say to them is to ask which is more important:
  75 that their library be well-constructed and use all the best technology
  76 available as free software, or whether it is worth degrading quality
  77 of their library in order to allow proprietary programs to use it !
  78
  79 To help the case of LGPL'd libraries for which adns is not a vital
  80 component - for example, a library which provides access to other
  81 libraries so that programs which use it need only use certain parts,
  82 I have released adns.h (just the public header file) under the LGPL as
  83 well as the GPL.  See the copyright notice in adns.h for details.
  84 Note that this will not help you if it adns is essential to the
  85 functioning of your library, because all programs using your library
  86 must link against both your library and adns and so must be GPL'd.
  87
  88
  89 For some information and views from the Free Software Foundation on
  90 free software licensing, visit:
  91
  92  Various licenses and comments about them
  93   at http://www.fsf.org/philosophy/license-list.html
  94
  95  Why you shouldn't use the Library GPL for your next library
  96   at http://www.fsf.org/philosophy/why-not-lgpl.html
  97
  98
  99 3. GPL-incompatible free software licences
 100 ------------------------------------------
 101
 102 Regrettably, there are a number of free software licences (and
 103 semi-free licences) in existence which are not compatible with the
 104 GPL.  That is, they impose restrictions which are not present in the
 105 GPL, and therefore distributing a whole work which contains both such
 106 a program and a GPL'd program is not possible: either the combination
 107 would have to be distributed under the GPL (violating the restrictions
 108 made by the original author), or under the GPL-incompatible licence
 109 (violating the GPL).
 110
 111 I may be prepared to make exceptions for such a licence.  Please
 112 contact me at <adns-maint@chiark.greenend.org.uk> with the full text
 113 of the GPL-incompatible licence.  However, I would usually prefer it
 114 if you could use a GPL-compatible licence for your project instead.
 115
 116
 117 -- Ian Jackson 17.9.2000
 118
 119
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