Meanwhile, Microsoft gets boned by Massachusets. Aside from the normal arguments for open source, I have another one specifically for governments. A democratic government works because any citizen can grab hold of the operation of the process, examine it, critisize it, and discuss it. In a proprietary environment, we can't examine the technical aspects of government operation. A great example is voting software- making the source open insures that an e-voting company is on the up-and-up. Wheras, if the source is closed, they could be fudging the results as much as they like, and no one would ever know (especially since audits are conducted randomly at individual locations, and there aren't many of them).
A citizen must have the right to examine and analyze ny part of government operation. Some parts require more expertise than others- that's why there are people called "lawyers". Portions of the government operation are complicated enough that it requires special knowledge and training. Much like analyzing software. It's not possible for a law to exist that is unknown, not in this society- at least not yet. For a law to be enforced and complied with, it must be known to everyone. For it to be modified, which is a key part of democracy, it must be available for analyzation. So must it be with the tools that are used to create, track, enforce, and modify those laws. All parts of the government process must be able to be examined.