I think that the complete name of MalwareBytes is Malwarebytes | Free Anti-Malware & Internet Security Software. Their website title is that too.
And from what I've seen, although their main product is free, they do have premium products / premium features too, mostly (but not only) for businesses.
I can see the difference now! Thanks a lot. Premium features which will make MalwareBytes more like ... an antivirus? more than the standard version which only scans and disinfects on demand. Or I should say more active
I don't know much more than you, since I only install MalwareBytes rarely and shortly, most of the time I use something else (firewall + on-access-scanning antivirus).
But since this thread was .. intriguing
.. I've done some research and I posted what I found out.