The NHunsell libraries uses the kernel32.dll which is not applicable for the mono framework, but there can be used libdl instead.
So The NHunspell dll must be refactored to use the kernel32.dll on windows system and to use the libdl on mac os and unix (all are mono) systems.
Additionally, the actual Hiunspell dlls must be compiled for those system as well (for mac os and unix libhunspell.so)
will be replaced by iTextSharp