CKAN is installed from source via ansible. Current version is 2.8.7. The installed ckan is modified with bugfixes or other needs not yet present in the current release. These are available as patch files in https://github.com/6aika/sixodp/tree/master/ansible/roles/ckan-install-patches. When CKAN is upgraded, installation of these patches most likely will fail. The developer needs to go through them and port necessary ones to new CKAN.
Most of the actual customization is done via ckan extensions. Some of them are implemented specifically for 6aika data portal, some are built by other with various degrees of modifications done in 6aika data portal. Below are lists of used extensions divided by responsible party of the extension.