From #openttdcoop wiki
World Wide OpenTTD Game Day
The world wide OpenTTD game day (WWOTTDGD for short) is based on a patch idea of Ammler, coming straight out of the needs of #openttdcoop: the community hit the hard-coded upper bound of 10 clients many times. Therefore, Ammler created [patch].
By now, the term stands for a compilation of patches in combination of #openttdcoop's GRF-Set. The project is mainly powered by dihedral, Ammler and Phazorx. Further details are available at the [dedicated page] on the [OpenTTD wiki].