I've got one of those hanging in my dojo, and you'll find nearly every Karate dojo in Okinawa has one hanging up. They usually give me a new one each time I go over and buy a Shureido NW3 gi.
You're correct in saying it is Bodhidharma, the text with it is the Kenpo Hakku. It is the concepts of Kenpo (in poem form) that stems from the Bubishi. This is a translation:
The Kempo Hakku.
The very important eight poems of the martial arts.
Jinshin wa tenchi ni onaji
The mind is one with heaven and earth
Ketsumyaku wa nichigetsu ni nitari
The circulatory rhythm of the body is similar to the cycle of the sun and the moon
Ho wa goju wo tondo su
The way of inhaling and exhaling is both hardness and softness
Mi wa toki ni shitagai hen ni ozu
Act in accordance with time and change
Te wa ku ni ai sunawachi hairu
Techniques will occur in the absence of conscious thought
Shintai wa hakarite riho su
The feet must advance and retreat, separate and meet
Me wa shiho wo miru wo yosu
The eyes do not miss even the slightest change
Mimi wa yoku happo wo kiku
The ears listen well in all directions
The traditional Karate guy, from an nontraditional background