But that is just an extensions. That is, the simple fact that OpenGL1.4 is supported does not ensure that vertex programs are supported.
But then why in the ARB_vertex_program spec does it say “Written based on the wording of the OpenGL 1.3 specification and requires OpenGL 1.3.”?
At the very least you need OpenGL1.3, because of multitexturing and stuff like that which appeared in the core of OpenGL1.3
ARB_vertex_program is an extension of OpenGL1.4 because the extension is mentioned in OpenGL1.4 spec (OpenGL1.3 spec never mentions vertex programs).
Anyway, it should not be a problem for developers : just check if the “GL_ARB_vertex_program” string appears in the string returned by glGetString(GL_EXTENSIONS) and you’re done. Additionaly you could check if glGetString(GL_VERSION) returns “1.3” or higher but you don’t really need to check that.