Time isn't the only corporate asset he could have utilized to create his competing code. He might have utilized corporate-funded computers, LAN hardware, Internet access/bandwidth, etc. When I worked for a major Internet corporation I signed a contract specifically stating that anything I created using any corporate resources belonged to the company. Thus, when I worked on open source stuff, I did it from home using my own computer on my own time. Did the author sign such a contract, or violate such a contract by using company assets other than business hours? We just don't know.