Unfortunately, taking a poll of people's opinions will not do you any good in this instance. FastTraxx is correct. Copyright laws are quite clear whether it is printed matter or someone working in a 3D modeling program. The creator of the works is the copyright holder and may distribute their work as they chose and distribute whatever rights to others that they chose. If an artist has specified that the model/obj is not for commercial use, but for personal/hobby use, then this is the right they are assigning by law. In case of commercial usage, the original author must be contacted for permission and/or a payment for use. Your age or inexperience will be not an excuse in a court of law. As an author (a vampire novel for sale on the web) and as an 3D Artist, I know about copyright. FastTraxx has been in the biz far longer and probably could quote you verbatim. Listening to his advice will probably save you a lot of headaches and possibly legal expenses if you are sued.