Which developers are a safe bet for longevity.

[Tj Shredder]

Its as mixed as with small or single developers. As soon there is a combination of a developer team and a huge user base, things change and they can surpass closed source projects. There is no contradiction between open source and commercial, not at all! The most used databases in the world are open source. (MySQL, MariaDB etc…) Even in closed source projects you pay mainly for the service and not only for the code.
With closed source you might get locked in and the company sucks you out at will, like Microsoft (or your beloved Apple) does this all the time… As long as they do a good job, you accept it, but you finance some super rich with it…

[BONES]

Hardly. I am yet to discover any open source project that surpasses commercial alternatives. Blender definitely comes closest but it is competitive, at best, and it's rapid rate of development actually works against it for professional use.

[Mike Janney]

We've been around so long now we're almost a church ...