One of the most important recent events in the world of free software has been the release of version 3 of the GNU GPL. There were fierce arguments about its utility while it was being drawn up, and although the rhetoric has abated somewhat, there is still a big question mark over its eventual success. Some evidence suggests that GPLv3 uptake is coming along nicely, while other reports indicate a reluctance to adopt it (but note also Matt Asay's neat reconciliation of these contradictory messages). To see what's likely to happen in the long term, it's useful to look back at the past history of licence adoption.