MSAA with deferred renderer extension for GL 2.1?

Are there any extensions that allows MSAA to be used together with a deferred renderer in OpenGL 2.1? I know there is a way to do this with OpenGL3, but we can’t use GL3 until Apple starts supporting it.

What feature of GL 3.0 allows the use of multisampling with deferred rendering? If it is multisample texturing, then this is available as an extension. Unfortunately, I just checked and the extension is written against 3.1 and GLSL 1.40, so it may simply not be available to earlier implementations.

There may not be anything you can do.

ARB_texture_multisample and ARB_sample_shading (see this, this, and this).

Now whether anyone exports these extensions in an OpenGL 2.x implementation is another story. The former is written against 3.1, while the latter against 2.0. So you’ll probably at least be missing the former.