The premise, though, was if a software company goes under. If you're talking about a non-compete contract, isn't it void at that point? If you're talking about copyrights/patents, I imagine that's another matter, since somebody would own those assets, even if the company is defunct.

In my experience in IT services, the main asset was owned by the customer. If the IT service company went under, I imagine the developers that were with the company would be free and clear to strike up a relationship with the old company's customers to continue service work on the software that was developed there.