Changes predating libungif 3.0 (news in the original libgif, in other words.)
is in ONEWS

Version 4.1.1
=============
* libungif is now available via anonymous cvs!  See the libungif web page,
  http://prtr-13.ucsc.edu/~badger/software/libungif.shtml
  for details.
* If you wish to join libungif development, please join the libungif mailing
  list.  Details on the libungif web page.
* Merge in many bug fixes that were sent in while I was hiking the
  Appalachian Trail.
* The libungif web page is being restructured.  Enter the site via this URL:
  http://prtr-13.ucsc.edu/~badger/software/libungif/

Version 4.1.0
============
* Several minor memory leaks in error conditions have been plugged.
* New Function EGifOpen(void *userData, OutputFunc writeFunc) allows user
  specified gif writing functions.
* Old copyright notices in a few source files have been updated.  All library
  copyrights should now reflect the copyright notice in the COPYING file.

Version 4.0.0
=============
Major fixes have been made to the code that handles Extensions.
Unfortunately, this causes binary incompatibility with giflib-3.0 and
libungif-3.x.  However, the API is still intact.  I am, however, deprecating
the use of saveImage[x].Function.  Use
saveImage[x].ExtensionBlocks[y].Function instead.

Version 3.1.1
=============
 The following bugs which caused SegFaults have been fixed:
 * When reading gif files with extensions, DGifSlurp would violate memory.
 * When closing a gif that had a local colormap, DGifCloseFile would attempt
   to free the colormap twice.
 * Fix a potential memory leak in DGifSlurp.
The following enhancements have been made:
 * New function DGifOpen to allow specifying a user definable gif reading
   function.

Version 3.1.0
=============
 * Add a new function:
        GifFileType *DGifOpen(void * userData, InputFunc readFunc)
   to read the gif image from a user defined input function.
 * A few bugfixes.

Version 3.0
===========
Changes from Eric Raymond's libgif:
 * A new gif encoder that makes uncompressed gifs rather than standard,
   LZW-compressed gifs.  This is actually the major motivating factor behind
   libungif; to provide third-party distributors a means to provide a gif
   library without the patented LZW encoder.

 * A new configure script to make compilation of the library on multiple
   platforms easier.  The package should now build shared libraries on all
   platforms supported by GNU libtool.

 * Removed the getarg functions from libgif.  These were not part of the
   public API and only used by the tools in the utils directory so I separated
   them from the rest of the library.

 * Fixed a few bugs in the tools in the utils directory.