Will tax billing software or water billing software ever be open source?  “Ever” is one of those word that’s often bandied around, so let’s limit it to the next 10 years.  There is a small market for public sector billing software, with a relatively small number of players, and a highly specialised sector knowledge required.  My guess is “unlikely”.  However it’s pleasing to see that in Australia Microsoft cash is being used to fund some open source development - see [1] this story from Down Under.