I've been using GCop for quite some time. It seems to me that the project is abandoned. Repeatedly described errors of the analyzer remain unsolved. The last commit and package were in June. In addition to this package, I now also use FxCopAnalyzers and StyleCop.
The question is - are you going to develop the GCop further or should we give preference to the other steadily developing analyzers (roslyn-analyzers project, stylecop)?