As professional software developer I appreciate the availability of open source software, especially if the license permits modifications and distributing these modifications. I try to use free software whenever I can and if time permits and there is a need, I help improving the software.
Some more examples are:
Much of my initial work was for the Amiga line of computers. DiskProtection is a block-oriented data encryption package. MakeCD is a very popular CD writing software, still in use and maintained today, but not actively developed anymore.