Self-employed business owner:
Students may start a business and be self-employed. In this situation, the student must work full-time (at least 40 hours/week). The student must be able to prove that he or she has the proper business licenses and is actively engaged in a business related to the student’s degree program.

Mr. Santoshgiri posted this information a while back:

Please also consider the following viewpoint of  attorneys, emphasizing that although self employed business owner provision exists, the 'Training' purpose of OPT 'without a supervisor' in self employed business and 'future continuance of the business' when the OPT ceases, makes it a shady area:
(Source: Mr. Santoshgiri's posting on Sajha)