I’m not in academia anymore (I esp. miss the field trips to the end of the world…) but instead have been working as a developer since many years.
That said, I fully understand your concerns. App lifetime & longevity is an often neglected issue. My impression is that many users feel that bigger companies guarantee better chances of longevity. But in fact, apps belonging to (or getting bought by) bigger companies have their own threats. If the app is just some product in the company’s product portfolio, it may not have the focus it needs. Or the new owner doesn’t really understand the product and its values. Or the company’s priorities change which may cause the app not getting attention anymore. Or, a company merger brings in a competitor and some top-level manager thinks that only one product can survive, etc. The above are all examples that I experienced first hand. There’s only perceived safety.
IMO, the ideal setting is often a small company (maybe 3 to 12 persons) where the app is the company’s only (or its major) product.
In any case, as a user, it’s good to think about exit strategies right from the beginning: