> Is there any good reason why the sources need to stay closed if they aren't going to make any further gains, financial or otherwise, from this product and its ecosystem?
I can think of lots of reasons. From a competitive point of view, you might risk having a big enough resurgence that it eats into the business of your replacement. From a technical point of view, it may reveal parts of the sausage making, or expose technology and libraries that you still use and rely on. From a legal point of view, it could open up multiple kinds of liability. From a support and staffing perspective, it typically takes at least a little time to open source something, if you want to do it well, there’s usually vetting & review by engineers and lawyers, and usually the need for more/better documentation than the internal docs.
Think about this from a business perspective- if they predict there’s going to be no financial upside, even indirectly, and there are costs and risks associated with it, then why would they? When companies open-source something, it’s not usually because the code is dead, it’s usually because the people in it are committed to open source and the org agrees to support that cause, or because the company stands to gain valuable attention from the community, and eventually or indirectly, profits.
We do have to support and celebrate when companies decide to release code, but we can’t really expect it or complain when they don’t, it just doesn’t make sense to them and they’re not obligated.