As of 10th January 2021 Ipponboard is fully available as open source. It can be obtained here: https://github.com/fmuecke/ipponboard
This decision was made because the last years have shown that I am not really able to invest my time in the further development of Ipponboard and the willingness to support the project via donations was rather low.
Therefore I decided to release the full source code to enable further development through the open source community.