In version 4.5 my zimlet would get the username of the logged in user using
PHP Code:
this.email_dropped_by this._appCtxt.get(ZmSetting.USERNAME);//getusername 
In Zimbra 5.02 this did not work. Using Firebug in firefox I saw the error. Searching through some of the new Zimlets I saw the following code
PHP Code:
this.email_dropped_by appCtxt.get(ZmSetting.USERNAME); 
This worked!

If anyone is using 4.5 and writing a zimlet, I am interested in if this code will work.

FYI, my zimlet is for pepperPM which is not yet released, I'm hoping it will be soon. I just have to get multiple email's to drag and drop, but I wanted to wait till version 5 to start that code.

I hope this helps someone.