Showkase can be purchased as Showkase-Standard (which comes with Juicebox-Lite and SimpleViewer-Standard, the free versions of the image viewers) or Showkase-Pro (which comes with Juicebox-Pro and SimpleViewer-Pro).
The only difference between Showkase-Standard and Showkase-Pro is the bundled viewers.
For example, if you were to purchase Showkase-Standard, Juicebox-Pro and SimpleViewer-Pro, you could integrate the Pro viewers into Showkase following the instructions here and you would essentially have Showkase-Pro.
When you purchase Showkase-Standard, you get a download link for only Showkase.
When you purchase Showkjase-Pro, you get separate download links for Showkase, Juicebox-Pro and SimpleViewer-Pro.
Purchasing Showkase-Pro is less expensive than purchasing Showkase-Standard, Juicebox-Pro and SimpleViewer-Pro.
However, if you have no need for SimpleViewer-Pro (the Flash image viewer), then purchasing Showkase-Standard and Juicebox-Pro separately (as you have done) is less expensive than purchasing Showkase-Pro.
If you want SimpleViewer-Pro, too, then the best option would for you to purchase Showkase-Pro and for us to refund you in full for your Showkase-Standard and Juicebox-Pro purchases. If you would like to do this, then please let me know and I will send you an email with further information.
If you do not want SimpleViewer-Pro, then there is no benefit in purchasing Showkase-Pro and you can just use your Juicebox-Pro files within Showkase.
How do I obtain JuiceboxBuilder?
JuiceboxBuilder-Lite comes bundled inside the Juicebox-Lite zip package and features only the Lite configuration options in its interface.
JuiceboxBuilder-Pro comes bundled inside the Juicebox-Pro zip package and features all Lite and Pro configuration options.
Juicebox-Lite and JuiceboxBuilder-Lite are free so you can download the Juicebox-Lite zip package from here and try it now.
I hope this helps to clarify things.