Switching between namecoin and bitcoin is as simple as clicking Tools -> Switch to, then choosing either Bitcoin or Namecoin. It's written in C# and requires the Microsoft .NET Framework 4.
You can change the target framework to something lower, like 3.5 or 2.0. Unless you're using .net 4 specific features. Also, you can autodetect whether a server is namecoin/bitcoin by issuing the "help" rpc command, and looking at the command list.
Why ? What do you mean ?
Are you trying to say it is a trojan or something ?
No, he thinks it doesn't look aesthetically pleasing, which i sort of agree. The gui has too many unnecessary elements, like moving money between accounts.
