Links to older versions of both JRiver Media Center and Media Jukebox can be found in the FAQ on Interact.
The latest version is always available on our Download Page. A newer, but possibly less stable build, may be available in a thread near the top of one of the boards on Interact.
You can Restore a License or have your licenses e-mailed to you from the Restore Page. You can also change your e-mail address there.
You can also upgrade if you prefer. Instructions are in a topic called "Upgrade to ..." on our Wiki.
JRiver Media Center for Windows
Media Center 18.0.212
Media Center 17.0.189
Media Center 16.0.181
Media Center 15.0.174
Media Center 14.0.165
Media Center 13.0.172
Media Center 12.0.534
Media Center 11.1.201
Media Center 10.0.173
JRiver Media Center for Mac
MC18 is available in a thread at the top of the MC18 for Mac board.
Media Jukebox 14.0.166
Media Jukebox 8.0.400