Berkeley DB Java Edition (with Clojure-wrapper available here) is pretty nice. The basic stuff is relatively straightforward, and should the need arise it supports replication and other high availability features. It seems that the license is more GPL-like than LGPL-like, so I think for closed-source applications (even without modifications to BDB JE itself), you'd need a separate license.
Berkeley DB Java Edition (with Clojure-wrapper available here) is pretty nice. The basic stuff is relatively straightforward, and should the need arise it supports replication and other high availability features. It seems that the license is more GPL-like than LGPL-like, so I think for closed-source applications (even without modifications to BDB JE itself), you'd need a separate license.