Group velocity dispersion is the change of group velocity with frequency as a signal propagates through a medium or structure.  In a waveguide it will include contributions from both material dispersion and waveguide dispersion.

Waveguide dispersion is the component of dispersion due to the change in mode properties (such as the mode field distribution) with frequency.

In general, waveguide dispersion and group velocity dispersion will differ.  Even when the material dispersion is zero, there can be a finite "profile dispersion" contribution to chromatic dispersion if the index contrast of the waveguide varies with frequency.  This can make it difficult to separate material dispersion from waveguide contributions.

Further to Vincent's reply, I would distinguish between the group velocity dispersion of a guided mode, and the group velocity dispersion of a plane wave in an infinite uniform medium, which I consider an aspect of material dispersion.

Like Vincent, I see no reason why these definitions should be any different for photonic crystal fibres.

The terms are the same for a Photonics crystal fiber. Your group velocity dispersion will contain contributions from both material dispersion and wavegiuide dispersion. The difference is that the photonic crystal gives you some extra tricks to play with in order to get the dispersion profile that you want.

In a standard step index fiber the core is defined by a refractive index step which is almost constant with wavelength. The effective index of the photonics crystal that defines the cladding of a PCF is wavelength dependent. This allows you a lot more freedom and in turn allows you to e.g. move the zero dispersion wavelength down to e.g. 800 nm.  and/or one can design a fiber to be endlessly singlemode so that it is singlemode at all wavelengths