This has been a frequent question recently, and the frequently-given answer is:
GNU support in uVision is now available via CodeSourcery. See: http://www.keil.com/appnotes/docs/apnt_199.asp
See: http://www.keil.com/forum/docs/thread12535.asp http://www.keil.com/forum/docs/thread12663.asp http://www.keil.com/forum/docs/thread12720.asp etc, etc...
My question is: if you've got Codesourcery - which includes a complete toolchain, IDE, debugger, etc - why would you also want uVision?