There are. The problem isn't the C++ bindings, it's that some GNOME library got deprecated. Similar, but different functionality, went into a GTK+ library (VFS kind of stuff). The deprecated old GNOME library became difficult to package because of dependencies it seems.
The porting is fairly trivial, but it's not mechanical. Referencer unfortunately uses things like the old URI thingy all over the place. By the 2nd day I got fed up and switched to Zotero.