Ripping a CD (or a DVD) is when you copy the tracks off the disk into another format. When you are using SoundJuicer (or Music Match in Windows)to import the CD, you're actually ripping the song.
There is a comment posted earlier here by someone from Codeweavers (too lazy to actually look it up) that they would have had to re-engineer the CD ripping and burning routines, they decided instead to release a version that supported playback, the iTunes music store, and iPOD. That's why you (and everyone else) get that message. Also, if it asks you to upgrade to 2.7 DON'T DO IT. It will break the iPod synchro. Just leave it at 2.6.
Sound Juicer won't rip to AAC as far as I know. Since iTunes and the iPod both play MP3, you can just do that (just crank the bit rate up a little). One thing I do when I'm ripping a new CD (very rare - I buy mostly from iTunes Music Store now) is kinda complicated but it works. I have a smaller HD with XP and iTunes on it (I have a laptop so it's very easy to swap HD). I rip (import) the CD with iTunes under Windows. I then copy the folder from my iTunes folder to my USB drive. Boot back into Linux, fire up iTunes and import the folder. Kinda complicated, but it works and it's in AAC format. You can also burn a DATA CD under the windows iTunes, copy it to your home drive in Linux, and import into iTunes.
Also, to keep my Linux and Windows iTunes in sync, I typically copy over the new folders/songs I have purchased to a holding folder on my USB drive and then import them into the Windows iTunes. (I also back up my iTunes folder to the USB drive - I'm paranoid).
Good luck and have fun - what Linux is all about :)