1. A method for managing an application execution environment, the method comprising: identifying which of multiple different versions of the application execution environment are installed on a computer; and managing the different versions of the application execution environment on the computer; wherein the identifying and the managing are performed using one or more of the different versions of the application execution environment; the application execution environment comprising a cross-platform application program interface to provide services to applications that run in the application execution environment, and the managing comprises managing the different versions of the application execution environment on the computer as a single runtime environment program having the different versions bundled therein; the method further comprising binding each of the applications to one of the different versions of the application execution environment; wherein the binding comprises: checking a namespace associated with one of the applications against the different versions of the application execution environment installed on the computer; installing a new version of the application execution environment on the computer when the namespace matches the new version, which is not already installed during the checking; and creating on the computer an executable for the one of the applications, the executable configured to load the version of the application execution environment that matches the namespace associated with the one of the applications.