Previously released versions of the code are available, but it is recommended to use the most recent version.
The current version 3.2 of the GPML code is available here.
Changes between versions are documented here.
The version 3.1 dated 2010-09-27 is available as gpml-matlab-v3.1-2010-09-27.tar.gz and gpml-matlab-v3.1-2010-09-27.zip.
The version 3.0 dated 2010-07-23 is available as gpml-matlab-v3.0-2010-07-23.tar.gz and gpml-matlab-v3.0-2010-07-23.zip.
The version 2.0 dated 2007-06-25 is available as gpml-matlab-v2.0-2007-06-25.tar.gz and gpml-matlab-v2.0-2007-06-25.zip.
The version 1.3 dated 2006-09-08 is available as gpml-matlab-v1.3-2006-09-08.tar.gz and gpml-matlab-v1.3-2006-09-08.zip.