An Obj file (as a generic document, not as a method of data storage) is also automatically copyrighted. Some software may strip out comments when editing/opening/resaving obj files, so it's necessary to include a readme file with the copyright notice, as well as documenting when you created the obj file and text file. Since thieves will delete the readme file when they try to sell the obj file, it becomes difficult to prove a violation unless you can get a copy of the suspected stolen obj file.