I run 10.6.8 and I am getting notices about installing Mavericks too.
I have not downloaded Mavericks, lion, etc. But I HAVE download the Mac AppStore. That was listed for me as a Software Update, in the usual way - via Snow Leopard's System Software Update app.
I do not buy software from the MacAppStore; I buy directly from developers, so I had and continue to have no need for the app store. And yet... I let System Software download it.
And I answered a Question as it was installed: something like...
"How's about I send you some notices about software you don't want and can't use on your machine? It won't even look like a REAL OS notice; no - it will look like a totally FAKE and Viris-ish, Trojan-like notice on your iMac! Cool, huh? See, it looks like a notice for a phone or iPad, though your iMac is not a phonePad, yet. And get this, it does not even say what App it is from! You will never know where it came from! Cool, huh? Want some notices? Say YES!"
And I thought, sure, why not? I already let Snow Leopard's system software update send me notices, why not the Mac AppStore too?
And there ya go... a couple weeks later - yesterday! - out of the blue... a small, unannounced, and ostensibly foreign and maybe intent on harm "you are eligible to install mavericks" notice appeared! Does that sound like a something Apple would do? Send a mystery notice?
Click YES or NO. What the...? Where did this come from? And if it is some bad thing, do both buttons actually send a "yes"? Why, if it IS from Apple, does it not NOT SAY SO across the top, like other OS system notices?? No way to dismiss it except to click a button.
Reading posts today I am learning it will continue to badger me, for no good reason, and I cannot turn it off since I do not have the AppStore's preference pane in system preferences, as others using a newer OS do. If you have that pane, click it and see if you can turn off the notices.
pestering... and looking like a virus or something while doing it too. Hateful. I am looking for its pref file .plist so I can toss that and run the app and MAYbe it will ask me the question again, "Want to get some pestering notices?" and I can finally say NO!
I will delete the app but I want those prefs gone first, against the next time I install this thing.