It's going to ship with a number of apps, including an Adobe PDF reader as well as access to the Rakuten Raboo ebookstore. It's not clear yet how open the device will be, but the press release suggests that it won't be as open as the usual Android tablet. I wouldn't expect to be able to install third-party apps.
Curiously enough, when Panasonic showed off this ereader a couple weeks ago they were calling it a prototype. This kind of turnaround indicates that they might not have been completely sure about releasing it, and the positive press may have changed their mind.