FSLeyes (pronounced fossilise) is the new FSL image viewer, released with FSL 5.0.10.
Download the latest version of FSLeyes for your OS here:
The source code for FSLeyes will be made available mid-2017.
If you are installing FSLeyes independently of FSL, simply unzip into a location of your choice.
If you wish to upgrade your version of FSLeyes which was installed as part of FSL (note: you may need to ask your system administrator to do this):
cd $FSLDIR/bin/ mv FSLeyes.app FSLeyes.app_backup unzip /path/to/downloaded/FSLeyes_osx_latest.zip
For Linux (e.g. CentOS6):
cd $FSLDIR/bin/ mv FSLeyes FSLeyes_backup unzip /path/to/downloaded/FSLeyes_centos6_latest.zip
If the newly installed version works, you may safely remove the $FSLDIR/bin/FSLeyes.app_backup ($FSLDIR/bin/FSLeyes_backup under Linux) directory.
User documentation for FSLeyes can be found here:
If you are having trouble getting FSLeyes to run, a solution may be documented on the troubleshooting page.
Under Linux, you may need to make sure that your system is up to date. For example, under CentOS6, you might need to run yum update as an administrator, before FSLeyes will work.