This service costs money, and someone has to pay for it. There is no getting around it. Basic groups are riding on the backs of those who pay, and their very existence cuts into groups.io's profit margin. By that measure, Mark is within his rights to place any restrictions on them that he deems necessary.
GMF and Group_Help actually contribute to the groups.io experience. These forums provide support so the proprietor doesn't have to. Other than that, I'm not very receptive to the notion that any group is providing such a public service that it should be exempt from contributing to the bottom line. As a group Owner, you either believe in what you're doing -- to the extent that you are willing to support it financially -- or you don't. Expecting groups.io as a business to pony up so an Owner doesn't have to simply flies in the face of logic.
Full disclosure: I do have a couple of Basic groups with grandfathered features. I also have a Premium group, for what that's worth.