Sharepod will download as a free demo with no time limit though with some transfer limits which can be unlocked if you upgrade to the full version by purchasing the app and registering it.
You can still transfer music to your computer in the demo of Sharepod 4, but it's limited to batch transfers of up to 10 tracks at a time. For the first transfer, you'll be able to transfer up to 50 tracks, but then all transfers after the initial 50 tracks are limited to 10 tracks at a time. By registering the app, you unlock unlimited, automatic transfer to iTunes, and you no longer will get the nag screens asking you to upgrade.
Sharepod 4 is a one-time payment for a lifetime license which includes all software updates to major version 4 and complimentary technical support for as long as you need it. The license will cover any of your personal iDevices and lets you install it on up to 2 of your computers at a time, Mac or PC, including any new ones.