Hi,
The AD8367's signal input (pin 3) presents a nominal 200 ohm resistance to ground -- thus it expects a ground-referenced input. If you're feeding it from a ground-referenced source (for example, the ground-referenced output of a transformer), there's no need to AC-couple the input. Note that this input can handle up to 700mV p-p, this implies it works with up to 0.35V above and below ground. It's not biased at Vcc/2.
If your input signal is riding on DC, then include a series capacitor to AC-couple the input. The eval board schematic does not include AC coupling, so its input must be without DC.
In contrast, the signal output (pin 10) is internally biased at VPSO/2 and must be AC coupled to a ground-referenced load. The VGA input (pin 5) accepts a 0.05 -- 0.95V, DC coupled input.
Best regards,
Bob