Dropbear contains a number of components from different sources, hence there
are a few licenses and authors involved. All licenses are fairly 
non-restrictive.


The majority of code is written by Matt Johnston, under the license below.

Portions of the client-mode work are (c) 2004 Mihnea Stoenescu, under the
same license:

Copyright (c) 2002-2020 Matt Johnston
Portions copyright (c) 2004 Mihnea Stoenescu
All rights reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

=====

LibTomCrypt and LibTomMath are written by Tom St Denis and others, see
libtomcrypt/LICENSE and libtommath/LICENSE.

=====

sshpty.c is taken from OpenSSH 3.5p1, 
  Copyright (c) 1995 Tatu Ylonen <[email protected]>, Espoo, Finland
                     All rights reserved
 "As far as I am concerned, the code I have written for this software
  can be used freely for any purpose.  Any derived versions of this
  software must be clearly marked as such, and if the derived work is
  incompatible with the protocol description in the RFC file, it must be
  called by a name other than "ssh" or "Secure Shell". "

=====

loginrec.c
loginrec.h
atomicio.h
atomicio.c
and strlcat() (included in util.c) are from OpenSSH 3.6.1p2, and are licensed
under the 2 point BSD license.

loginrec is written primarily by Andre Lucas, atomicio.c by Theo de Raadt.

strlcat() is (c) Todd C. Miller

=====

Import code in keyimport.c is modified from PuTTY's import.c, licensed as
follows:

PuTTY is copyright 1997-2003 Simon Tatham.

Portions copyright Robert de Bath, Joris van Rantwijk, Delian
Delchev, Andreas Schultz, Jeroen Massar, Wez Furlong, Nicolas Barry,
Justin Bradford, and CORE SDI S.A.

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation files
(the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge,
publish, distribute, sublicense, and/or sell copies of the Software,
and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT.  IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE
FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

=====

curve25519.c:

Modified TweetNaCl version 20140427, a self-contained public-domain C library.
https://tweetnacl.cr.yp.to/

Contributors (alphabetical order)
Daniel J. Bernstein, University of Illinois at Chicago and Technische
Universiteit Eindhoven
Bernard van Gastel, Radboud Universiteit Nijmegen
Wesley Janssen, Radboud Universiteit Nijmegen
Tanja Lange, Technische Universiteit Eindhoven
Peter Schwabe, Radboud Universiteit Nijmegen
Sjaak Smetsers, Radboud Universiteit Nijmegen

Acknowledgments
This work was supported by the U.S. National Science Foundation under grant
1018836. "Any opinions, findings, and conclusions or recommendations expressed
in this material are those of the author(s) and do not necessarily reflect the
views of the National Science Foundation."
This work was supported by the Netherlands Organisation for Scientific
Research (NWO) under grant 639.073.005 and Veni 2013 project 13114.