I donated in the past. Now I upgrade to Yosemite and wanted to upgrade Libre Office.
It seems that downloading is impossible without a donation.
Heve I made a donation (still have the screen image of the confirmation of payment).
But nothing changed: I still found no control to start the update (or the download of the .dmg).
What to do?
The download page has lots of automagic to give you the last stable release on your platform, but in case something goes wrong, you can always go to Index of /libreoffice/old and get any release for any platform for completely free. 
Hope that helps.
Your browser might block the download (redirection). Just click on the download file in the donation page (top left area) and it should work.