If upon opening 'darktable' v2.0.7 on Mac OS X 10.6.x (Snow Leopard)
results in very small font, open the following file...

~/.config/darktable/darktablerc

...using a text-editor. Add "font_size=12" if not already there and
change "screen_dpi_overwrite=-1.0" to "screen_dpi_overwrite=96".

The reason for "-1.0" as the default is to attempt to use the system's
DPI but darktable may not be able to do it correctly.

The higher the DPI value, the larger the text.

And yes, even a Mac OS X system may have a "~/.config" directory just
like a GNU/Linux system, especially if free and open-source software
is installed. The easiest way to get there is to have a Finder window
opened and then SHIFT+COMMAND+G to navigate there. Your system may
even have 'nano' installed if you want to edit the rc file within the
Terminal.app.