The old version of QLink is based on the QDBM database engine.
The last release of QLink in this version was on July 2008. Still, the package will be available on the site. I strictly recommend moving the new version of QLink, however it does not work under Windows.
Download the package. It contains both the source and the binaries for Linux32, Linux64 and a Windows version with a pack of dll files.
To compile QLink one needs to have QDBM and Mathematica developer kit installed.
The old version of QLink uses both file-based databases (up to 2GB) and directory-based databases (up to 2GB times the number of open files). This version turned out to be unstable when the number of open files grows large, hence I recommend moving to the new version.