[Fyren]

The error about OnDependenciesDropped is because the code is years old and that function has since been added to one of the SM interfaces. You will either have to compile against an ancient version of SM or update the code.

The orangeboxvalve branch of the hl2sdk is obsolete. It was for first-party Valve games that shared engine code (or close enough), but those games diverged and the SDKs were split out.