Latest official version of JDemetra+ version can be found at
https://github.com/jdemetra/jdplus-main/releases/tag/v3.0.2
For installing instructions see https://github.com/jdemetra/jdplus-main#installing.
Note that Java 17 is now embedded is in the installation files, you don’t need to tackle this issue on your computer. Be sure to choose the windows specific zip file (if you use windows).