In an open letter to IBM, Ian Tree asked IBM to open source Notes/Domino. An interesting request but there is a very simple reason why this is not going to happen.

Too much work. Not enough return.

People underestimate the amount of work it takes to open source an existing code base. Stormy Peters explains in more detail what the problems are/will be.

It reminds me a little bit of the OS/2 fans asking the same thing in 2005 when IBM announced it would end support for their operating system. It didn't happen back then and it won't happen now.