Looks like there's some misunderstanding about "commercial use."

As I understand it, it means using the item in a render/animation/print that is sold commercially. In that case, I assume "free" means "free". If the freebie maker allows commercial use in this sense, he/she cannot expect any financial compensation.

Selling the item itself? That is just plain simply not allowed. An item may be marked for "commercial USE". Downloading a freebie and then selling it as if you made it yourself, that's not commercial use, that's a direct and plain copyright violation.

In the marketplace, 'rosity has a standard EULA. If you buy something at the MP, you can use it according to the rules laid down in the Renderosity EULA. The vendor may grant the buyer additional rights, but as far as I know, he/she cannot take away rights granted by the 'Rosity EULA.

Something similar might be useful in the freestuff section. A Renderosity standard freebie EULA for non-commercial use and a Renderosity standard freebie EULA for commercial use - which one appliies is up to the freebie maker, Additional rights can be granted (in a readme, for example), but don't have to be.
That way, when you download a freebie, you know exactly what your minimum rights are, so the kind of nasty surprise the OP encountered is eliminated.

The pen is mightier than the sword. But if you literally want to have some impact, use a typewriter

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