With a very few exceptions, when an author distributes a model, even for free, they retain legal rights to the model. Essentially, they're granting you a license to use the model in your own work, but not to redistribute the model. Some authors are really specific in their accompanying files about what you can and cannot do with or to their property. Others are not so specific (pariticularly those who don't provide readme files with the model), but specificity doesn't change the basic, inherent intellectual rights issue you ask about. In both a moral and legal sense, I'd suggest that your best bet would be to seek permission from the original author before redistributing their work whether in a different format or not. If you can't locate the original author, you're probably better off to move on; find a model for which you can locate the original author and get permission there. If somebody has put a model up on the web for free, they're likely to be receptive to having that model available in as many formats as possible, so they'll probably say "sure!" when you ask. You're pretty much free to do whatever you want to the model for your own use; it's when you redistribute it (even without any profit motivation whatsoever) that you run the risk of hitting legal snags. I hope this helps. - Dex