To download the most recent development version go here.
Alternatively you could go to the MathWorks central file exchange here.
A zip file for the current release can be downloaded here. Please cite the current release as: Kevin Mattheus Moerman. (2016). GIBBON (Hylobates Lar). Zenodo. 10.5281/zenodo.44404. Go to: https://zenodo.org/record/44404 to import the citation into a citation manager (e.g. Mendeley).
Go here to navigate to the GIBBON GitHub page where you can set-up GIT or SVN version control to stay up to date with the latest development.
For Linux various GIT options exist, and for SVN one could use RabbitVCS.
After downloading the code follow the “installation” instructions to make sure the help and documentation is integrated properly into MATLAB.