"I expect to spend much of my life being paid to write software, and I just don't see copyrights has helping me in anyway." you are going to let people take your software for free. Could you tell us who's going to pay you? Debian guys are fed up by Ubuntu's hardworking people who's selling services to companies. Fedora is not continued. RMS is probably good in programming, but to say the understanding to human nature and society, he's just naive and pathetic.

anyway the company can sue you, but they would most likely lose unless one of the following fact stands: 1. they patented partial of full feature set 2. they patented some key technology (not necessary the implementation) in the tech tree 3. they had non-compete term with you, which is unlikely since you are only engineers and you are seriously thinking about compete so most of the time, you are safe. but the value of software is in the service and maintenance. I don't see dominant privileges from making a less bug version. why customer choose yours instead of your company's version?