I am thinking of putting eJukebox on my external hard drive so that I can play my music with either my desktop or laptop computers. Would I need more then one subscription to do this?

For that to work (using the same eJukebox installation on the external drive - on different computers) you would have to do a full eJukebox install on each computer. Then you would ignore those installations and run ejukebox.exe on the external drive.

This requires 2 licenses, one for each computer eJukebox is used on. After you activate the licenses you can freely use the external drive's eJukebox.exe while on either computer.

Not twice. You just order one - 2 computer license. When you do that you get 33% off the total (which works out to between $10-$20 for the additional computer). That will allow you to stay registered on both PCs at the same time. Otherwise, with just a single computer license, you would have to Remove the license from the other PC and enter your account password to activate the current PC each time you switch between the 2.

Note: If you order one eJukebox Pro license and activate it on one computer you can freely use the 2Web feature from any and all other computers. No extra licenses are required to access the 2Web browser interface on other PCs.