Question

Is there a way to have one window display more than one terminal at once? (Not in the typical tabbed configuration, more like a grid of arbitrary number of terminal screens)

Ideally I'd like to have a 3 column by 2 row window with 6 terminal instances in the one window.

An application with this as a feature is preferable.

Answer 1

There is Terminator which comes as a Debian package.
Maybe you can get it working on your Mac (use the source).

Answer 2

GNU Screen for Mac can do this:

Answer 3

Use a tiling window manager with multiple terminals to arrange them quickly and easily in any such configuration. Use a workspaces feature that is in almost all linux window managers to switch between that layout and other window layouts (like regular maximized apps). I prefer xmonad. Another nice feature of a tiling window manager is that you can remove the titlebars from those 6 windows to remove wasted space.