Catalogablog reports that there is a new open-source integrated library system in development in Japan. It's called Next-L Enju Leaf 1.0.0, and you can see a demonstration of it here. Catalogablog reports that it is in use by the National Diet Library, and the National Institute for Materials Science.
It also appears to be related to other OS ILSs called the Next-L Enju Root and the Next-L Enju Flower, but I do not know what those are like.
The developer is Project Next-L, described as "a project to build a new integrated library system maintained by Japanese volunteers interested in libraries"