It hadn't even occurred to me to look for it on the App Store. I went to check, and noticed that it's $9. Since the reviews suggest that it's not always kept up to date there, and since part of that $9 is going to Apple, I wonder what the advantage of installing through the App Store is over installing directly and donating $9 to the Document Foundation?
Good reminder, just went to the doc foundation and donated a bit. I've been using LO (and OO before) for ages, remiss not to pay it back at all. Thanks!
Edit: I installed via the App Store. Double-clicking a file in Finder works but opening from within LibreOffice does not.