I've just looked at http://wiki.maemo.org/Documentation/..._UI_Guidelines and I don't see anything about them having to be the same width...?
Widgets must be as compact in size as possible; even though Maemo 5 offers a generous amount of screen space, users must be able to place several widgets on each screen to minimize the need for excessive screen switching. N.B. Due to the high pixel density of the physical screen, tappable elements must be at least 70x70 pixels in size for convenient finger use.
Widgets must be designed to be as compact in their size as possible, avoiding any excessive graphical elements that do not provide any meaningful information or controls. As a rule of thumb, the footprint of a Widget must never exceed half of the Desktop space allocated for Widgets, including a 24px‐padding around the Widget (132,352 pixels total). The largest stock Widgets, Location and RSS, are close to the maximum footprint of Widgets, as seen in Figure 4; another, Tutorial, spans across the entire Desktop, but therefore remains limited in its height.