You can get almost everything needed to build the emulator by using the [Play! Build](https://github.com/jpd002/Play-Build) project. You can also checkout every repository individually if you wish to do so, but make sure your working copies share the same parent folder.
- Open the newly copied `ExternalDependencies.mk` and change paths inside to point to the proper dependency/repository paths (ie.: `/path/to/boost` -> `C:\Libraries\Boost`)
To build for those platforms, you need to first build boost using the [script](https://github.com/jpd002/Play-Dependencies/blob/master/BoostMac/boost.sh) provided in the [Dependencies](https://github.com/jpd002/Play-Dependencies) repository. This will create the boost Xcode framework files that are needed by the projects from this repository. Once this is done, you will be able to open `Play.xcodeproj` for either OSX and iOS and build the project normally.