It's for Lab126, the division within Amazon responsible for the software on the Kindle. Currently the Kindle does have a Web browser but the general consensus is that it sucks. This job posting describes what sounds like is a position to help build a new, "innovative" Web browser for the device.
The browser would likely not be issued for the current generation of Kindles but be included withe the next edition, which is rumored to be announced later this year. This new Kindle is expected to have a full color touchscreen, as a few weeks ago Amazon bought New York-based Touchco, a company that makes multitouch full-color LCD screens. Touchco is being integrated in the Kindle hardware unit.
That, coupled what we know so far about Amazon's own Kindle app store initiative, means that Amazon is treating things like the Microsoft Courier and the iPad as real threats. The addition of a Web browser is a no-brainer, but what remains to be seen is how good it is. Safari on an iPhone (very similar to how it should hold up on an iPad) is surprisingly easy to use. And the new version of Internet Explorer Mobile is a vast improvement over it's predecessors. Amazon is going to be entering a crowded market here.
But, hey, it's a job. Anyone hiring anyone is good news right now. And with the way the mobile device wars are rapidly heating up we'd be surprised if this is the last one. It's going to be an interesting year, and we're making popcorn for it.