If we decide to use a piece of open sourced software that is currently released under a license that allows inclusion in an internal closed source system, what protection are we offered if the owners of the open source software decide to change the license? Typically I'm thinking of where the new license does not allow inclusion in closed source software (I think the PDF generation api iText did this back in 2009).
Can the new license be applied retrospectively to the old versions? I'm guessing it can, but often isn't. We are just looking at worst case scenario, would we be in a position where we could just continue using an old version for as long as it suited and then make a decision about the future - or would we be in a position where we'd have to decide to either pay the commercial fee that is often available or find a different "free" alternative.