Java's original intent was to allow developers to write programs and it is supposed to run in any OS without the need to change your code. Hence, it's slogan "Write Once Run Anywhere" . Unfortunately, Java was not really able to fulfill this promise. It is widely known that the different JVMs (Java Virtual Machines) are incompatible with each other. This is what Adobe AIR promises to solve. And so far if you run Adobe AIR applications like Klok, you will find that it will run exactly the same whether you are using Windows or Linux. I cannot however answer with regards to Mac. Because right now it appears that Apple, Inc. is not very fond of Adobe, Inc.