As with any project, assessing the Return of Investment for porting an application must balance the expected advantages against the cost. There are two different cases where porting promises to be profitable:
If your company uses its own proprietary applications in production, it might be able to capitalize on the quality and flexibility of the mainframe hardware. It can also take advantage of zSeries features like virtualization, HiperSockets, the cryptographic facilities, or the 64-bit architecture. It might also be able to use the mainframe's virtual communication methods to achieve a closer integration of the application in an integrated server environment. See Chapter 19, "Building Integrated Server Environments."
There is a growing demand for Linux applications for the mainframe. If you are a software vendor, having a Linux-on-the-mainframe version of your application can be a decisive competitive advantage. A number of major software vendors already have ported some of their strategic software to Linux on the mainframe.