Before the legalese starts, here's the translation to plain english:

  1. Do whatever you want with paintlib. Just don't come running to me with a lawyer if something goes wrong.
  2. If you redistribute paintlib, you should redistribute the whole library including documentation and copyright. If that is not possible, you must make it clear that you're distributing a changed version. In no event may any part of the library be distributed without this copyright notice.
  3. If you use paintlib in your program, you must acknowledge this, preferably in the about box and the documentation.

The legalese itself is a derivative work. I modified the LIBPNG copyright notice. Thanks, guys :-).

The paintlib source code and all documentation are copyright (c) 1996-2002 Ulrich von Zadow and other contributors.

The paintlib source code is supplied "AS IS". Ulrich von Zadow and other contributors disclaim all warranties, expressed or implied, including, without limitation, the warranties of merchantability and of fitness for any purpose. The authors assume no liability for direct, indirect, incidental, special, exemplary, or consequential damages, which may result from the use of paintlib, even if advised of the possibility of such damage.

Permission is hereby granted to use, copy, modify, and distribute this source code, or portions hereof, for any purpose, without fee, subject to the following restrictions:

  1. The origin of this source code must not be misrepresented.
  2. Altered versions must be plainly marked as such and must not be misrepresented as being the original source.
  3. This Copyright notice may not be removed or altered from any source or altered source distribution.
  4. Executables containing paintlib or parts of it must state that the software "contains paintlib code. paintlib is copyright (c) 1996-2002 Ulrich von Zadow and other contributors.". This notice must be displayed in at least one place where the copyright for the software itself is displayed. The documentation must also contain this notice.

Note that libpng, zlib, libtiff and the jpeg library have their own terms of use. You can find these in the documentation of the libraries.