Everywhere in the world wide web, one can see different platforms and publications of OpenFOAM® tutorials and related topics. If one uses the published training cases, videos or publications that Holzmann CFD provides under the GPL v3 license, make sure that you play fair and add the reference to your source. Taking credit for others achievements does not agree to the GPL v3; see the statement of Hrvoje Jasak. Please respect the GPL v3 and also the time I spend into the different kinds of published work - it is really a lot and I already saw some really similar cases I provide at Holzmann CFD.
If one uses some libraries for commercial usage (means selling simulations such as results with the openComfort library), one should be fair enough to denote and support Holzmann CFD.