Is libreoffice free for commercial use?
Yes - but note that there’s no free technical support offered (except for peer-to-peer help resources like this one, without any guarantee).
Yes you are right, if you define “free=no cost” - but there is another aspect and this is “license”. And related to license it is not free of a license (MPL v2.0), which has a binding nature to the user of LibreOffice (I know about discussion of Free Software, OpenSource etc, their respective differentiation, but just want to point that commercial users need to abide by an agreement like all users of LibreOffice)
yes it’s free for commercial using