svn co svn://svn.appwork.org/utils AppWorkUtils
svn co svn://svn.jdownloader.org/jdownloader/browser JDBrowser
svn co svn://svn.jdownloader.org/jdownloader/trunk JDownloader
svn co svn://svn.jdownloader.org/jdownloader/MyJDownloaderClient MyJDownloaderClient
ant -Dbasedir=JDownloader -f JDownloader/build/newBuild/build_standalone.xml
You have to check out the listed svn repositories above and then can run the build_standalone.xml ant buildscript.
(Note: can be compiled with Java 1.8 up to current Java 26, ant script targets java 1.8)
You will then find the compiled standalone build in JDownloader/standalone/dist directory.