Important: they replace navigation, not Apple's data
All three apps use OpenStreetMap data and downloadable offline maps. They offer search, turn-by-turn navigation, and trail maps, but not live traffic, Look Around, or the business information of Apple Maps. Search quality depends on what contributors have mapped in your area.
Organic Maps, CoMaps, and OsmAnd
Organic Maps is the simple option, with offline maps, navigation, GPX support, and CarPlay and Android Auto. CoMaps is a community-governed fork of Organic Maps with a not-for-profit focus, developed on Codeberg. OsmAnd is the most configurable, with extensive routing, contour lines, custom layers, and outdoor modes, but a more complex interface.
License and pricing details
Organic Maps and CoMaps are Apache-2.0, and OsmAnd's code is GPLv3, with some artwork under a proprietary license. OsmAnd's free version limits map downloads to 16 files and leaves features such as Wikipedia POIs and contour lines to paid options, while Organic Maps and CoMaps are fully free.
Platforms and CarPlay
All three run on iOS and Android. Organic Maps supports CarPlay and Android Auto. Apple Maps itself is available on iPhone, iPad, and Mac, so Mac users will not find a desktop equivalent among these apps.
Maintenance status
Organic Maps, OsmAnd, and CoMaps were all updated within the past days. CoMaps' main repository is on Codeberg, with the GitHub repository only a mirror.