Tunnelblick is built to run on OS X 10.4 through 10.9, and on both PowerPC and Intel processors. It is built using Xcode 3.2.2 because that is the last version of Xcode which produces PowerPC code. (It is built in a virtual machine.)
If you want to build Tunnelblick using a newer version of Xcode, that's fine, but it won't run on PowerPC computers, and there may be problems because it will be built as a 64-bit application, and the code was not written for that. I assume you will get warnings and/or errors from the Xcode compiler.
At some point Tunnelblick will drop support for PowerPC processors, at which point it will be updated to build on a later version of Xcode. There are not current plans for this, however.