We're just about to create an Octave-Ngspice interface package. The idea would be to use the shared library of Ngspice. For building the package the user will definitely need the Ngspice-library installed. The problem is however that the library is fairly new, so there are no distros (Linux, Cygwin, MinGW, Solaris, BSDs, etc.) out there providing the necessary binary development package. This implies that
1. the user has to build and install the library with the corresponding header files into a specific path, or
2. the build framework of the Ngspice Octave-package shall attempt to download, build and install it (assuming that all the dependency libraries have already been previously installed). Building the library takes quite a few minutes on an average computer.