I've been using v1.4.6 for years, with "mysql" backend. It is stable and quite straightforward to code with, simpler than interfacing MySQL directly. The unperceivable efficiency loss it may introduce is more than compensated by the ability to support different backends as needed. It supports multi-statements, so a query loops through results, rows, and columns. I suggest configuring it with --disable-utils, --enable-singlelib, and --disable-shared in order to be free to try new versions and still obtain a compact executable. The scarse activity on this project is possibly due to the fact that it just works. An alternative to this is Libzdb, which seems newer. I found no reason to switch, though.