The question is not which version of GLSL SFML uses (if at all, because if you don't run the Shader example it doesn't touch GLSL in any way) but rather why it would matter. If you only use SFML for context management, input, audio and the other things without touching the "Graphics" part of it, it doesn't render anything at all. You are in charge of controlling what OpenGL would do in that case, and if your hardware supports GLSL 4.40 (which you should know how to check) then you can use it. Since you seem to want to go that route, you can also request that a 4.x context be created for you if you want to restrict yourself to the non-legacy OpenGL API.
