Anyway, on OSX, neither Photoshop CS5 and presumably CS6 as well, would open them, and neither would Graphic Converter, which was quite the surprise.
Happily, turns out that on OSX Lion and Mountain Lion iPhoto handles them OK, certainly iPhoto 11 or v9. Drag all the .pcd files into iPhoto, add them to an album, and then Shift-Command-E to export them.
Memo to self: you don't need to spend money on software such as this.
On Linux, I found that since I can run Photoshop CS2 under WINE, they open absolutely fine: