Wanderstories has created their own topographical map source by contributing data to OpenStreetMap. This data is then leveraged by using Mapbox to create the end result - a Wanderstories styled tile.
OpenStreetMap creates and provides free geographic data, such as street maps publicly. The project was started because most "free" maps actually have severe legal or technical restrictions on their uses, holding back people from using them and the data in creative, productive, and/or unexpected ways.
OpenStreetMap data and the maps from this site are available for free. But OpenStreetMap totally relies on the input of it's users, so please consider contributing GPS traces and/or by mapping your surroundings if you find this service useful.
Nearly all the data used in this map comes from OpenStreetMap contributors, like myself. OpenStreetMap is open data, licensed under the Open Data Commons Open Database License (ODbL).
Mapbox makes it easy to leverage the data from OpenStreetMap and create the end styling. Therefore, attribution includes © Wanderstories, © Mapbox, and © OpenStreetMap.