There's been quite a few updates to the HDM-JOSM style, a map style for JOSM developed by HOT focused JOSM users who are mapping in developing countries and areas that have experienced humanitarian or natural crises. Find more about the HDM-JOSM Style at this June blog post
Since the initial version that was released in June, we've made several improvements to it, mostly bug fixes
and improving the color scheme so that it is easier to see and trace objects for all kinds of satellite imagery (wetlands, desert, and urban areas)
If you're using JOSM that is newer than version 6152, Just Select HOT/HDM in JOSM's Available Map Styles List (Located in JOSM Preferences
Those that are using a version older than 6152 will have to manually add the map style and use this different link http://ubuntuone.com/252trPHQ7upvvFXtcAXLF5 due to a bug in older versions of JOSM
Your version of JOSM appears at startup launch screen if you don't know your version.
We encourage your contributions and feedback on our github page