Well, it's infrastucture. Moreover, it's infrastructure for infrastructure! So if that sounds super boring you don't have to be excited :-)
But I would tell the story something like this: state storage is the root of (almost) all operational evil. It's very easy to make a system reliable if it's totally stateless. Even most bugs can be lived with if the worst you have to do is restart a service and carry on! But to do anything interesting you have to store state somewhere, and you have to modify that state concurrently without screwing it up.
And the many challenges of operating stateful systems are greatly multiplied if you have a lot of different ones. For example, if you have a datacenter outage and some but not all of your stateful systems deal with it correctly, probably your application as a whole is still down.
So as one more stateful system, does FoundationDB just make that worse? Well, FoundationDB is designed specifically to be a foundation for many very different stateful systems - not just different kinds of databases but things like search engines or message queues that you normally don't think of in the same category. So that almost any system can map to it efficiently, it has a lowest common denominator data model (key/value) and the highest possible guarantees in terms of concurrency control. And you can run diverse systems supporting an application on the same FoundationDB cluster, or on different clusters with the same exact operational requirements.
Some few users of FoundationDB have been able to get the benefits of this vision, consolidating lots of different stuff into a single, operationally desirable system. But for more people to be able to, not just does the key/value store have to be available to them, but also lots of stuff has to be built on top of it. By releasing FoundationDB under a very liberal open source license, Apple has hopefully made that possible. In the long run, hopefully it will make all server-side computing more reliable.
Also, it's a really good key/value store, if you happen to need one of those!
