Requisites

Install java jdk from packages

$ pkg_add jdk

Installation

Download JDownloader.jar from jdownloader page

Create directory

$ mkdir -p ~/bin/jdownloader
$ cd ~/bin/jdownloader
$ mv ~/Downloads/JDownloader.jar .

Usage

$ /usr/local/jdk-17/bin/java -jar $HOME/bin/jdownloader/JDownloader.jar