No, I don't think the icons are Aliases. In OS X, don't the Aliases have a little arrow at the bottom left of the icon? The icons I'm talking about look like little hard drive or device icons. I thought they were just the installer apps, but stuff tends to stop working if I toss them.

I didn't even know I had a Receipts folder, so I've certainly never removed anything from it. I learned my lesson about OS X and messing with the System folder that one time when I tried to mess with it like it was still OS 9. I'll never do that again.

If I really feel that I must do something of that nature, I'll ask someone who knows more than me or I'll RTFM.