The only thing free about it is the price.

So think of them the same way you think about the purchased models.  You have the same license rights as the purchased ones.  You have the right to perform the model for life.  You have an unlimited right to distribute the model in open source games as long as they are not easily accessible to the end user.

You DO NOT have the right to post the model al la carte and separate with the open source game as a mash up for instance.  If you want to do something like that simply put a turbosquid link to the asset to let the end user themself agree to the EULA and download the asset.

It may seem silly since it's free, but sometimes authors change their minds later and want to sell them.  Because they post them free for now here that doesn't mean they want you to distribute the model as if you were their agent.

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