I have character models which are exported from a PC game, it is legal to sell it ?
No. You can’t just copy movies and sell them legally, can u?
You need a license or agreement to use “whatever”, if it’s interlectual proberty of an other person/company.
As long at the license allows you to do so you can. Check the Derivative Works section of that license and see what it says it will spell it out for you what you can and cannot do.