Copyright
The source for the Shapefile C Library is (c) 1998 Frank Warmerdam, and released under the following conditions. The intent is that anyone can do anything with the code, but that I do not assume any liability, nor express any warranty for this code.

As of Shapelib 1.2.6 the core portions of the library are made available under two possible licenses. The licensee can choose to use the code under either the Library GNU Public License (LGPL) described in LICENSE.LGPL or under the following MIT style license. Any files in the Shapelib distribution without explicit copyright license terms (such as this documentation, the Makefile and so forth) should be considered to have the following licensing terms. Some auxilary portions of Shapelib, notably some of the components in the contrib directory come under slightly different license restrictions. Check the source files that you are actually using for conditions.

Default License Terms
Copyright (c) 1999, Frank Warmerdam

This software is available under the following "MIT Style" license, or at the option of the licensee under the LGPL (see LICENSE.LGPL). This option is discussed in more detail in shapelib.html.

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.

Shapelib Modifications
I am pleased to receive bug fixes, and improvements for Shapelib. Unless the submissions indicate otherwise I will assume that changes submitted to me remain under the the above "dual license" terms. If changes are made to the library with the intention that those changes should be protected by the LGPL then I should be informed upon submission. Note that I will not generally incorporate changes into the core of Shapelib that are protected under the LGPL as this would effectively limit the whole file and distribution to LGPL terms.

Opting for LGPL
For licensee's opting to use Shapelib under LGPL as opposed to the MIT Style license above, and wishing to redistribute the software based on Shapelib, I would ask that all "dual license" modules be updated to indicate that only the LGPL (and not the MIT Style license) applies. This action represents opting for the LGPL, and thereafter LGPL terms apply to any redistribution and modification of the affected modules.
