Counting is not so easy.
With respect to download counts, Linux users normally get their copy of LibreOffice from their distro, either as part of the default install or from their standard repos. I believe that most of the major distros ship LibreOffice, not Apache OO. Linux users have little or no reason to get their copy directly from the LibreOffice site. This means that a major part of LibreOffice's user base won't show up in their download counts.
Then there are derivatives and rebranding, such as NeoOffice, which can also make difficult to get accurate user base figures for either LibreOffice or Apache OO.
Biting the hand that feeds IT
