JDownloader does not have a memleak. It can only use max memory. If you say your whole system gets sluggish then it is very likely a memlean in firewall/av/other tool. For example we know that some av tools have issues with sparse files and killer network driver have a memleak ,
https://support.jdownloader.org/Know...emleak---crash
You can check about dialog of JDownloader to check how much memory java is max allowed to use