The 3.5.3 is a technical release made after the transition of Carrot2
repository to github.com/carrot2
It does not introduce any new features other than an upgrade of SWT
which updates Workbench to SWT 3.7.1 and makes it usable on newer Ubuntu
and possibly other Linux distributions.
For a complete list of improvements and bug fixes, see JIRA
issues fixed in version 3.5.3.