Netpbm consists of code contributed by many authors. In every file of
the source code, there is a copyright notice, telling you what you may
or may not do with the code. All authors have granted you the right to
use and distribute their code without having to pay them, as long as
you meet some simple requirements.

Most of the components require you to include a copy of their
copyright notices and warranty disclaimers in any copies or
derivations you distribute.

Another restriction that some of the software has is that in order to
have permission to copy it (which includes writing anything derived
from it), you must distribute source code for your copy or derivation
and propagate the same restriction to people who would copy your
derivation.  In other words, the price the author wants for the use of
his proprietary work is your contribution to the free software cause.

One component prohibits you from selling it or using it in a
commercial way: hpcdtoppm.

Some components are contributed to the public domain.  

The copyrights on individual components of this package are detailed 
at appropriate places within the package.


PATENTS
-------

These are the patents the Netpbm maintainer knows about that relate to
Netpbm.  It is basically just information the maintainer has stumbled
over at some point -- no search has been done.

No licenses have been granted by patent owners to the maintainer of
Netpbm.  Therefore, if you need a patent to use something in Netpbm,
you need your own license.

A note about patents in general: A patent gives an inventor the
exclusive right to make, sell, or use the invention.  If you
independently invent something without knowing that the patent holder
already did, that makes no difference -- the patent holder still has
the exclusive right.  It makes no difference if you give the original
inventor credit.  The patent applies to a method, not its expression,
so writing a program from scratch to implement a certain method is
still a patent infringement.  Infringing a patent is not a crime per
se, but to the extent that it costs the patent holder money, the
infringer has to make it up.

The original purpose of patents is probably perverted when patents are
applied to things you implement in computer programs.  This is one of
the Free Software Foundation's causes.  See 
<http://www.gnu.org/philosophy.html#laws>.


Unisys owns a patent on LZW compression, which is used by ppmtogif,
and maybe on LZW decompression, which is used by giftoppm.  IBM also
owns a patent that may cover the GIF tools.  Unisys offers a license
of the patent for trivial use for $5000.  Its patent expires in 2003.
Neither company has ever enforced the patent against trivial users of
it.  <http://news.cnet.com/news/0-1005-200-1713278.html> is an 
article dated April 18, 2000 on the issue.  
<http://www.unisys.com/unisys/lzw/> is Unisys' view of the matter.
For information from another perspective, see <http://burnallgifs.org>.

The following Netpbm components may be restricted by this patent:
ppmtogif, giftopnm.

A good substitute for GIF if the patents are a problem is PNG (see
pngtopnm, pnmtopng), which was developed with a primary purpose of not
using any patented technology.

You can also use the -nolzw option on ppmtogif to avoid using the LZW
patent.  The images so generated are larger than traditional
LZW-compressed GIFs, but any GIF decoder can decode them just the
same.

The jbigtopnm and pnmtojbig programs use arithmetic coding patents and
other patents covering various aspects of the "front end."