On the Mac, if you are working in another application and use the mouse to switch to Sibelius 6 (or earlier versions) by clicking anywhere on your score, your click will not actually do anything other than switch your Mac’s focus to Sibelius, which may be exactly what you want.
However, in Sibelius 7, such a click will immediately be active in the score; for instance, if note entry is active in Sibelius, and you’re working in another application, one click on the Sibelius window will place a note in your score, which you may not desire.
This is known as “click-through” (which is different than the web traffic term “click-through rate”). If you use Sibelius 7 but prefer the non-click-through behavior in Sibelius 6, download and install Klicko, a System Preferences panel. It runs in 32-bit mode, which means you’ll have to open System Preferences twice (this does not mean that Sibelius or any other program will run in 32-bit, just Klicko).
Set up your preferences as follows, and you should be good to go:
If anyone knows of similar behavior and/or solutions on Windows, please feel free to leave a comment.