Single-vendor open source projects are somewhat common, but are they actually “open source” in any useful sense of that term? It’s often said that open source is as much about community as code, but in a project with all committers and maintainers sitting behind the same firewall, there’s no real contributor community. So why bother with open source at all?
The first reason may have nothing to do with community, but everything to do with posterity. According to Steven Rostedt, “To allow their product to continue even when the company is gone. How many times have you lost good products due to the company failing? That is what builds trust with your customers.” Or, perhaps put another way, if the code is open source, the customer need not trust the developer of the code. The license doesn’t guarantee that the code will be well-maintained, but it does guarantee its availability.