I understand this might be confusing.
There is the “Enterprise Free Edition (CFE)” which is similar to Enterprise Standard, but limited to 25 hosts in monitoring and no distributed monitoring. This uses the proprietary Checkmk Micro Core. So you may want to call it “free as in free beer”. Than there is the “Raw Edition (CRE)” which uses the less efficient open source Nagios core. This can be used without limitations. It is “free as in free speech”.