If I use any of the AppleLoops supplied with Logic 9 in my project, will I be subject to an liability or royalty? If yes, how can I reach those persons who lent their voices to the loops?
All of the AppleLoops supplied with Logic or purchased via JamPacks are licensed to you for unlimited, perpetual use in any derivative creative work. That is: you can use the inside of your own music, but you can't just give away or resell the samples themselves.
For example: if you made a "song" that was one AppleLoop, looping for 3 minutes, and tried to sell that. Well, that's not really a derivative work because it's just the loop and nothing else. You couldn't give that away or sell it. But combine two of them together? Now it's derivative (it is unlike either of it's pieces, a new thing unto itself) and you can give that away or sell it as you, the creator, see fit.
B. Except as otherwise indicated, you may use the Apple and third party audio file content (including, but not limited to, the Apple Loops, built-in sound files, samples and impulse responses) (collectively the “Audio Content”), contained in or otherwise included with the Apple Software, on a royalty-free basis, to create your own original soundtracks for your film, video and audio projects. You may broadcast and/or distribute your own soundtracks that were created using the Audio Content, however, individual Apple loops, audio files, sound settings, samples and impulse responses may not be commercially or otherwise distributed on anor may they be repackaged in whole or in part as audio samples, sound files, sound effects or music beds.
Enjoy those loops! Make lots of awesome music!