Linux port of the software based on its latest available version. The software reportedly utilizes portions of Wine to function, so it wouldn't be accurate to call it an actual “port”. As a result, there are a few features missing in this release due to Picasa relying on certain Windows components.
Picasa 3 Beta is also available for Windows now, which is no surprise, but not for the Mac. We wonder if this is some sort of trend setting at Google, let's remember that the company's month-old Chrome browser remains at large a Windows-only application.