The press release is worth a read:
Kibera remains a blank spot on the Kenyan map, though it holds as many as one million inhabitants according to UN-HABITAT. Its limited health and water resources, traffic patterns, and housing layouts remain largely invisible to the outside world and to residents themselves. Though many organizations have collected data on Kibera, the information is not yet shared as a resource for all to use. Map Kibera will fill in this gap by producing free, open-source digital map data using the techniques of OpenStreetMap, a user-edited map of the world. The resulting information will be freely available to residents, NGOs, private companies, and others interested in working with and for Kibera.