build: make LGPL mode final (via --enable-gpl)

Rename --enable-preliminary-lgpl2 to --enable-gpl. This concludes the
relicensing. Some things are still to do (relicensing some still-GPL
optional code), but we consider the code included by --enable-gpl to be
fully relicensed.

The relicensing was performed by asking every known author for
permission for relicensing it to LGPL version 2.1 "or later". If an
author could not be contacted or permission could not be obtained, and
the contribution was considered relevant for copyright purposes, the
affected code was either excluded from LGPL mode (not built), or removed
or rewritten. This is the standard in open source relicensing processes.

Keep in mind that using LGPL mode is still on the user's own risk. Even
though I claim that the relicensing was pretty clean and thorough
(measured on the standards of the open source community¹), and I
followed the advice of some actual experts, there is still a residual
uncertainty due to the fact that I'm not an all-knowing entity (authors
could have taken someone else's code and pretend it's their own) nor a
lawyer (meaning I might lack associated authority or expertise), and the
fact that the judicial system is far from deterministic. The relicensing
was performed merely to the best of my knowledge. I reject all
responsibility outside of that.

This commit also cleans up the "Copyright" file to reflect the finalized
relicensing process.

¹ Not to imply that the standards of commercial companies are much
higher. Some major tech companies get away with stuff I would not
consider clean.

See #2033.

1 files changed, 4 insertions, 4 deletions

diff --git a/wscript b/wscript
index 8d99e82a62..b50d278d41 100644
--- a/wscript
+++ b/wscript
@@ -27,14 +27,14 @@ Dependency identifiers (for win32 vs. Unix):
 
 build_options = [
     {
-        'name': '--preliminary-lgpl2',
-        'desc': 'Preliminary LGPLv2.1+ license',
+        'name': '--lgpl',
+        'desc': 'LGPL (version 2.1 or later) build',
         'default': 'disable',
         'func': check_true,
     }, {
         'name': 'gpl',
-        'desc': 'GPL build',
-        'deps': '!preliminary-lgpl2',
+        'desc': 'GPL (version 2 or later) build',
+        'deps': '!lgpl',
         'func': check_true,
     }, {
         'name': 'libaf',