The
Open Look Window Manager.
The window manager that came with
OpenWindows, and is now part of the
xview applications distribution available for many
Unix variants.
olwm combines the ugliness, clumsiness and relative slowness (on X) - of the Open Look GUI with the lack of features of the first window manager, twm.
Ugliness is obviously a matter of taste, but I never liked the sight of Open Look's icons and menus.
The clumsiness is mainly in the slowness and the amount of screen real estate taken by icons and menus. Open Look is quite customizable (if necessary, through X resources) but it can't be made lean enough to my taste. A clumsiness particular to olwm is that window placement is non-customizable: new windows are always placed 'cascading', which means that for an application that opens many windows in sequence (e.g. an xv used to view a hundred images), you keep chasing the new windows around the screen, unless you explicitly tell the app to open its windows on a fixed display position, which requires knowledge of X resources.
Compared to other window managers, olwm has a few oddities in its X session control, e.g. it uses a olwmslave process. This is related to its support for Tooltalk, the (horribly broken) OpenWindows interapplication communication system.
A feature sorely lacking in olwm is virtual desktops, which is more than enough reason to switch to olvwm.