Hmmm. Good job I’d already decided to move away from using Gallery and the WPG2 plugin to manage images here. As both WordPress and Gallery are moving targets, so to speak, it’s important that WPG2 gets updated to match, otherwise at some point it will break, and there will be much weeping and wailing.
Realising that it will be a while before I can switch off WPG2, I thought I’d make sure there were no upgrades available or imminent. A bit of searching showed that sites formerly associated with the project were no longer running, but I soon found the project page, which contained the notice:
With the upcoming Gallery3 changes, I no longer have time to develop the WordPress/Gallery2 plugin (WPG2) and will provide no further versions. Feel free to take over the project.
Which means that unless someone does take it over, sooner or later it will fade away, and only be useable on old versions of Gallery and WordPress.
 Gnashing of teeth optional: please consult your dentist first