What part of it is closed-source? You can clone it from the SVN, even the MyJdownloaderClient and all plugins are open-source. Only thing that sucks are their docs because its a Google Doc and there isn't really any explanation but I've got a plugin to work via AI.
Not all plugins are open source. Some of them are included in the jdclosed dependency which is just a blob. The developers claim this is to prevent sites from patching them. However this approach is not compatible with the GPL and the developers have simply been ignoring this for years.
