JDFeedMe is free, and requires JDownloader, which is also free. Before you download the JDFeedMe plugin, you have to install JDownloader and check which version of JDownloader you have.
JDownloader Stable (Version 0.9.580)
This is the current stable release of JDownloader.
JDownloader Nightly (Current Beta Version)
JDFeedMe is already included with the newest beta version of JDownloader, so no download is needed. If you want to learn more about Nightly, check out the JDownloader forum.
JDFeedMe is in beta version and is currently being developed. If you encounter a bug, please report it (as a comment for example), so the development team can start fixing it. Also update your JDFeedMe version from time to time since new versions are being released.