From Homestar Runner Wiki
The Cheat's new computer, Monosodium Dreams, debuted on July 10, 2006 in the email redesign. It apparently replaced Tangerine Dreams. It is modeled after the design of Apple's iMac G5 or Intel iMac desktop computer, but with the Tandy logo on it, and a slightly different interface. While Strong Bad wonders why this computer only has half a monitor, the entire computer, as the one it is modeled after, is a single unit, using an LCD display rather than a CRT as older computers did (thus Strong Bad's comment). He also mistakes the wireless mouse for a plastic bar of soap. Mike Chapman jokingly came up with the name during the commentary for redesign.
The font used for the menu bar is Chicago, and while the default font for OS X is actually Lucida Grande, Chicago had been the default since System 7 and was also used on the original iPod. The lack of information on the menu bar and atop the windows that have been seen so far suggests that the image or animation is apparently "Picture Clipping", an image opened by the Finder with no usable extension. However, such an item can be copied to the clipboard, which then can be pasted as a new image by many available graphics editors.
Also, suggesting that this is the Finder, at least version 10.4, the menu bar has been modified.
Monosodium Dreams' Finder Menu Bar:
Mac OS X Tiger's Finder Menu Bar:
The menu bar is missing the Spotlight icon at the right of the menu, the Apple logo menu at the left of the menu, and the application name in bold afterward. The "Help" menu (which is the last menu) the "Go" menu (before the "Window" menu), and the "Edit" and "View" menus have been switched around compared to Finder v10.4's menu bar. Its gradient is also off, with dark gray to gray instead of white with a light gray gloss.
Also, unlike the iMacs it resembles, the iSight at the top of the computer is round instead of square, and it appears that there is no mic to the left of it, nor a status light for the camera. The menu bar is also not round as in Tiger; however, in Leopard, the menu bar takes on the square appearance.