So, I have finally succeed with rembrandt : I've updated my OS Snow Leopard (10.6. to Mountain Lion (10.8.2), downloaded XQuartz 2.7.4, and all is running fine.
With the old version I couldn't compile three frag files (ssao.frag, blur.frag and sunshine.frag), due to an unexpected compilation error : the compiler didn't accept to initialize array of float, as mentioned in the log report, although the syntax was correct regarded the OpenGL Shader Builder reference manual (???).
10.6.8 :
For the two files blur and sunshine it was possible to initialize the values of the arrays manually and to compile they. But for the ssao file, I was not able to initialize the v[4] of type vec2 :
const vec2 v[4] = vec2[](vec2(1.0,0.0),vec2(-1.0,0.0),vec2(0.0,1.0),vec2(0.0,-1.0));
Now in 10.8.2, all is ok (it runs also with 10.7.5 as mentioned by Philosopher here above).
So, for me, the problem is solved.