Mac OS X supports vertex programs and shaders on all renderers. GMA 950 has no HW TCL so all vertex transform (programs, shaders and fixed function) is in software.
If you want, you can get the current renderer ID with either CGLGetParameter(ctx, kCGLCPCurrentRendererID) or with glGetString(GL_RENDERER). But there are better ways to do this.
If you want to know if a given renderer supports hardware TCL, you can look at kCGLRPGPUVertProcCapable via CGLDescribeRenderer (this is false on GMA 950.)
Since vertex shaders can fall back to software emulation on all hardware when they exceed hardware capabilities, it might be better to detect if your specific shader is running in software emulation. CGLGetParameter(ctx, kCGLCPGPUVertexProcessing) will tell you this.