I have unique knowledge/experience about how a variety of industrial equipment and computer systems communicate, and how the software to allow them to communicate should be designed. Right now, it's very difficult to make these devices/systems communicate, but at the company where I work we're creating software which uses the knowledge I have to greatly simplify the process. Companies have happily paid us large amounts of money just for the beta version of our product. I'm currently the only active developer.

On the one hand, there is a need to protect critical portions of this code. But in an ideal world, there would be some way to profit from the useful software we're creating while opening source access to the world. I would absolutely be open to ideas about that, or experiences people have had.

At the very least, I would like to avoid internally segregating our code base for future developers. However, how would we prevent a VC funded competitor from poaching one of our developers and gaining access to knowledge it would have taken them years or decades to acquire?

Are some businesses only viable with closed source, internally segregated, software? Or, is it inevitable that all source will leak anyway, so you should try to create a model which does not rely on proprietary information?