Recently i really was amazed by openstreet maps, and it's very possibilities to manipulate data, aswell the free of charge about many prescious things - like geocoding and the maps itself.
But i wish to still having a backup behind with google maps.
Is it possible to having both of them in Flex, and how ? ( or at least where i can look for similar project of "unification" )
It appears that OpenStreet Maps has a REST API. You can access that API in a Flex application using the HTTPService; assuming a proper crossdomain.xml file is in place.
If not; you'll have to use a proxy between your Flex app and the REST API.