ZTree uses 7-Zip's archive engine for archives, and 7-Zip's SFX module for
self-extracting ones (Windows programs):

  Opened, viewed and extracted: 7z, zip, rar (and rar5), tar, gz, bz2, xz,
  cab, iso, lzh, arj, wim, dmg and the other formats 7-Zip reads,
  passwords included.

  Created (F5, Ctrl-F5): zip, 7z, exe (a self-extracting .7z, for Windows),
  tar, tar.gz, tar.xz and tar.bz2; zip, 7z and exe can be encrypted. 7-Zip
  cannot create rar, cab, iso, lzh, arj, dmg or the other formats it only
  reads: those need their own program named in ARCHIVER.BB2 (a RAR program
  for rar).

  7z.so       7-Zip 26.00's Format7zF library, built unchanged from 7-Zip's
              own source (7z2600-src.tar.xz, SHA-256
              3e596155744af055a77fc433c703d54e3ea9212246287b5b1436a6beac060f16)
              with ztree's 7zip/build-7zso.sh
                https://www.7-zip.org
                https://www.7-zip.org/a/7z2600-src.tar.xz
  7zCon.sfx   7-Zip 26.04's 7zCon.sfx for Windows (its console SFX module),
              unchanged: put in front of the .7z in an .exe made by Ctrl-F5,
              it unpacks the archive by itself on Windows (7-Zip's Linux
              source has no SFX module)
                https://www.7-zip.org/download.html

7-Zip is Copyright (C) 1999-2026 Igor Pavlov, and is distributed under the
GNU LGPL; the RAR decoder in it under the GNU LGPL with the unRAR licence
restriction, and a few files under BSD licences. Its licence, with the
unRAR restriction, is in LICENSE.7-Zip.txt next to this file. The source
of this 7z.so is the archive named above; of 7zCon.sfx, 7-Zip 26.04's.
ZTree itself is not covered by that licence: it loads 7z.so at run time,
and copies 7zCon.sfx into the archives it is asked to make
self-extracting. A self-extracting archive carries 7zCon.sfx, under the
same GNU LGPL; the files packed in it are not covered by that licence.

Without 7z.so, ztree still runs; archives then need the external programs
ARCHIVER.BB2 names. Without 7zCon.sfx (or 7z.sfx), Ctrl-F5 offers no .exe.
