I tried to uninstall this by deleting it, but the AppStore still thought that it was installed. I deleted some preferences files in my /private directory, which made the AppStore "forget" that I had installed Xcode. I used the following command:
sudo find / -iname '*xcode*' 2> /dev/null | egrep '^/private.*' | xargs -I file sudo rm -rfv file
Which deleted the following files from my computer:
/private/var/db/receipts/com.apple.pkg.XcodeMAS_iOSSDK_6_1.bom
/private/var/db/receipts/com.apple.pkg.XcodeMAS_iOSSDK_6_1.plist
/private/var/folders/7d/n34963zx62s7znxyzn3dn6bh0000gq/C/com.apple.Xcode.503/CachedSpecifications-Xcode
/private/var/folders/7d/n34963zx62s7znxyzn3dn6bh0000gq/C/com.apple.Xcode.503/CachedSpecifications-xcodebuild
/private/var/folders/7d/n34963zx62s7znxyzn3dn6bh0000gq/C/com.apple.Xcode.503
I do not know what these files are used for, but it made the AppStore forget that it was installed, which is what I needed to happen. In my case, the AppStore was not allowing me to update to the new version of Xcode.