I was able to get this working on my QNAP TS-431. This one has a Armv7 in it. My QNAP does not have optware readily available like some of the other ones. For instance, optware doesn't exist in the app center. I originally had entware-ng installed but I got the same error as Cornstrike. I was able to get this issue resolved by uninstalling entware-ng and installing an unofficial version of optware found **External links are only visible to Support Staff**here. The forum that I found that optware did not recommend using it for many packages. I assume that it's possibly unstable on systems like mine. After I installed it however, the jdownloader script ran flawlessly.

Chryses,
I would be happy to test some scripts for you using the entware-ng. Ideally, I would like to give you vpn access to my nas but my ISP switched some systems over and now my router is on a private ip. So I can't open any ports until that gets resolved. If you are really interested however, I could probably set up a laptop with teamviewer or something for you to get access here. Like I said before, I have a QNAP TS-431 which includes a Armv7