back in 2009, for version ESXi 3.5, the same question was answered that the base license is free, that thread also quotes matching licensing terms.
My intention is to offload some VMs from my laptop with a paid/commercial VMWare Fusion Pro purchased under the assumption that the answer has not changed. I'm totally aware that the free basic hypervisor has technical limitations.
My actual issue is the current EULA: When I followed the download link in my case for 6.7, now 7.0 Download VMware vSphere Hypervisor for Free the download page referred to a very different EULA. Key quote: "limited right to use one copy of the Software in object code form in a non-production environment and for a limited time period for the sole purpose of evaluating" which clearly differs from the previous answer.
My experience with the evaluation was negative in so far that hosted by my laptop's Fusion Pro, ESXi 6.7 would not successfully install nor boot any Mac guest VM, tried in various versions (10.7, 10.13) and various ways with Installer ISOs, OMV, OMA, Fusion upload of working VMs and so forth, where Fusion itself would run all those test VMs.
Before I retry the ESXi evaluation with a clean install, version 7 rather than 6.7 on an ageing Mini Server from the compatibility matrix, I'd prefer to re-ask the initial question:
Is there still a current (i.e. 7.0) basic free version of ESXi that allows for commercial use - in production environment for unlimited time, and how would I find that.
I'm not aware of change in free Hypervisor license limitations.
In the past there's been a note below the license key - once registered - that the free license key may be used with up to 99 hosts.