Many hard engineering fields see the impact of their work on the environment directly. Using sustainable materials in your products implies that they’re better for the environment than they might otherwise be. How does this translate to software engineering?
Certainly, there are the direct contributors. The maintainers of the linux ACPI kernel module that allow computers to hibernate in S3 processor state are having a direct impact on energy consumption in computers. Xen and VMWare are saving companies money and energy by reducing the number of computers needed for a particular task. Writing efficient code could be viewed as ‘green’ because you’re (in theory at least) using less energy and producing less heat to perform a calculation.
Centralized processing and repeated where many users display the result of a single calculation instead of calculating it themselves could be considered green. Binary software distributions are a good example of this. Software that must be updated frequently, (like a kernel) should be compiled once and then distributed to all the systems that will use it.
I’m sure there are other things that would improve the ‘greenness’ of software. Any suggestions?