Pash is a multiplatform PowerShell implementation.
The main goal is to provide a rich shell environment for other operating systems as well as to provide a hostable scripting engine for rich applications. The user experience should be seamless for people who are used to Windows version of PowerShell.
The scrips, cmdlets and providers should runs AS-IS (if they are not using Windows-specific functionality). The rich applications that host PowerShell should run on any other operating system AS-IS. Secondary goal: the scripts should run across the machines and different OS's seamlesly (but following all the security guidelines).