Here, Martin Brandenburg says it is not true that "Every short exact sequence of the form $0 \to A \to A \oplus B \to B \to 0$ splits." Then Mohan says in comments that "As a positive result,
If $0 \to A \to A \oplus B \to B \to 0$ is an exact sequence of finitely generated modules over a commutative Noetherian ring, then the exact sequence does split."
Mohan adds as an answer to my comment "The proof, while not trivial, can be worked out and I would be happy to post one somewhere (how?) if you so desire."
Now Mohan and other friends can you please...
Thank you.