Fosm.org (website) is a of the OpenStreetMap database, designed to keep the CC-BY-SA license (OSM's data license before the switch to ODbL in September 2012) and thereby keep all the data compatible with it.
It is a work-in-progress, although the data and a limited read/write API are already running. It is possible to configure JOSM to use the fosm.org server for downloads and uploads of data. It is also possible to use Merkaartor with patches applied https://github.com/fosm/fosm-merkaartor.
There are patches for the revert scripts https://github.com/fosm/FOSM-revert-scripts.