I've seen Enterprise projects become open sourced in the past and the biggest problem that they face is that no community builds around them. It is not trivial to get other folks to hack on your project and contribute code or use your code, it takes some marketing (hackernews, reddit, etc) and a lot of patience and answering questions. For most projects I would not bother open sourcing them, because trying to build a community around them can be just as much work as what was spent coding them in the first place, but there are a few gems that I would if I could.
It depends. If this isn't a hypothetical question, more details would help answer it.