I tried to install PowerShell 3 (Windows Management Framework 3.0) on Windows 7 Starter edition and got a message saying "The update is not applicable to your computer". I was able to install by extracting the CAB and using pkgmgr.exe. Everything seems to work fine. Another user had it happen on Windows 7 Home Premium, and he also got it working the same way. See his blog post, here: http://darekpagesedge.blogspot.com/2012/11/instalacja-powershell-3-ise.html
Are these OS versions really not supported, or is there an over-restrictive launch condition on the update package?