In that case it would be just as easy to have the OSS app be used directly by the closed source app instead of spinning up another service. It could be a librar

In that case it would be just as easy to have the OSS app be used directly by the closed source app instead of spinning up another service. It could be a library, a plugin, or even just a separate app that your internal app shells out to. Basically, a separate OSS release really shouldn't be a consideration for deciding to run it as a separate service or not. Though it is an excellent reason for a separate repo.