Ubooquity server is free for non-commercial use.
Ubooquity server requires Java 8 (Oracle version).
It is probably already installed on your computer. Otherwise you can download it here.
Ubooquity is not yet compatible with Java 9+.
Version 2.1.2 - 14 october 2018
If you find Ubooquity useful and want to support its development, you can donate using Paypal.
Thank you !