I have push a new branch, "complex", to the github repo.
You must set -DPETSC_COMPLEX=ON, and the complex version of the interface will be built.
(Compiling will throw an error when it tries to compile against a real PETSc installation when this is turned on, or if it finds a complex one when it is turned off)
You can have the real and complex interfaces installed at the same time, one will be called "ngs_petsc" and the other "ngs_petsc_complex".
Unfortunately:
1) You cannot load both at the same time
2) When you a complex and a real PETSc installation at the same time, you have to be careful with your LD_LIBRARY_PATH/PETSC_ARCH/PETSC_DIR environment variables! For me, loading ngs_petsc when the complex libraries take priority will not produce an error but garbage output!
Best, Lukas