This is just a plain old NSWindow
. It's not textured. You can set a title with setTitle:
in code or the Title field in the IB inspector. Tweetie's window doesn't have a title because the developer chose not to give it one.
The bottom bar is created by setting the content border on the window. Look under the Size tab in the IB inspector. (Uncheck "Autosize" and put in a value.) You can also pick "Large bottom border" from the popup menu in that tab and have IB set it up for you.
You can add a label in Interface Builder. Just type "label" into the Library filter search box and it will come up.