bmwtechguy said it best I think.
"API license and starburst means the oil meets the minimum requirements for the spec, such as chemical limits to protect emissions systems, lower viscosity for energy conserving, Noack volitility limits, cold cranking, HTHS, wear protection, shear stability etc. Also, oil companies pay dearly to have their oils licensed, tested, etc. and pay some type of royalty per gallon or quart over a certain amount sold. Non-licensed oils may be better than the spec in some or every way or worse. You have to decide if you trust the company blending/selling the non-licensed oil."
Can also be said of mfg approved oil.
I sure as hell don't trust synlube. They've gone out of their way to make sure I don't.