Yeah, it probably wouldn't be honored unless the company did something to indicate they sanctioned your actions. Your second scenario, in which the company leaves it up for a year, may go a little ways towards creating apparent authority. However, if you had no prior connection to Microsoft, the court would probably say a reasonable person would not believe you had the authority. Even if you were a Microsoft employee, because it's Windows 8 in particular, the bar would be pretty high for showing that a reasonable person would actually trust the authenticity of this open source license.