Update: Luis Villa was kind to converse with me via email and noted that the AGPL’s language speaks only to networked software as a service. Therefore, while the AGPL may be a good choice for web-based voting, it may not work at all for traditional e-voting machines. A similar-in-spirit license with slightly different wording may be needed (I’m wondering if one exists). Of course, the better approach would simply be to legislate disclosure of the code and the best might be to ban electronic voting altogether.
My question to the peanut gallery: what sort of license would you select for a bright, shiny new voting system project and why?
Lots of mention of the GPL in the comments of that post but it nor any permissive free software license (or the public domain) is appropriate. The GPL does not require disclosure of modifications made to the machine-installed version as the software is not being propagated. Therefore, the software on the machines could be different than the version(s) voters download to audit. To serve democracy, the voters must be able to audit unmodified copies of the software actually used on the machines. A license that will do this is (not necessarily – see update above) the Affero GPL. It would force exact copies of the software used on the machines to become available to users of the machines.
And on a related note, electronic voting needs free software as a service but that’s not enough. A tangible record (e.g. paper) is also necessary as free software doesn’t necessarily prevent tampering of the machines in the possession of those the public must trust.