This project worked for me, and here is what I did:
1) Downloaded the git (as a zip) to my Windows 10 Pro system
2) Extracted the project, opened "completed" in IntelliJ
3) Removed the Maven
config and only used the Gradle config
4) Ran the project.
I only know some Gradle and I don't know Maven.
From what I understand is they should both be able to do the same job, however Gradle is a little newer.
I know that there are some changes that you may
need to make to your configuration files (Maven/Gradle) if you are using a version of Java
other then Java 8.
Maybe if you try out the Gradle version of this project it will work for you?