The source-code of the webapplication and the implemented algorithms can be viewed in the DBIS-Git. It is also possible to report bugs here::
https://git.uibk.ac.at/dbis-isochrone/isochrone
https://git.uibk.ac.at/dbis-isochrone/isochrone-web

A tool that allows to update the underlying data with some help from OpenStreetMap and publicly available transportation schedules is also available (isochrone-datamodel). Besides this tool there are others as well (isochrone-tools) which handle the computation of node densities in a given range and the creation of synthetic networks that can be used for testing:
https://git.uibk.ac.at/dbis-isochrone/isochrone-datamodel
https://git.uibk.ac.at/dbis-isochrone/isochrone-tools

Some test data that can be used to calculate isochrones, is also available (it is delivered as a database dump). The data in this dump has been created from OpenStreetMap and from a GTFS-Export provided by the SASA located in Bolzano (a local transportation company). A PostgreSQL database (with the PostGIS extension enabled) is needed to work with it. The data can be found at the following location:
https://dbis-owncloud.uibk.ac.at/index.php/s/kgjm3CItQJ6P374

The research described here is highly connected to the research which takes place at the Free University of Bozen/Bolzano. The publications made by the people of Bolzano are available at a dedicated website, which is available here:
http://www.inf.unibz.it/dis/projects/isochrone