The outstanding question though is that in this type of case, high-end domain specific software, the pure open source model tends not to produce the ultra-high end software. The reason, though it seems to mystify many open source advocates, is that it takes lots of money to make a unique or novel thing on time spans of less than a decade...and the only way to recoup those costs is by selling that thing at some price and keeping the IP closed. Multi-thousand dollar plugins are one example.
In other words, going open source in this type of sense means that you won't have the latest and greatest anyway. So your particular case example doesn't change things.
Doesn't explain why the software couldn't revert to Open Source once that company goes defunct. If I were running a large company, I would think about asking for such terms.
It's actually really nice when it happens. There are cases though where the source code does not actually compile into the complete product, typically where lots of third party components are licensed in.
In other words, going open source in this type of sense means that you won't have the latest and greatest anyway. So your particular case example doesn't change things.