MapServer
6.4#21 in gis softwareFree planFree planWebAPILinuxmacOS
VisitMapServer suits developers and organizations building web maps from geographic data who need support for the listed formats, standards, and deployment environments. It is also a fit for teams able to manage a free, open-source engine.
WorldWind is for developers building geospatial applications and organizations visualizing geographic data. Its web and Java options cover browser use as well as Windows, Mac OS X, and Linux.