I am looking to create a piece of software, and will need to hire/collaborate with a developer, but I am unsure what language I should be looking for.

Some of the basics:
-Will run on a NAS device(probably a linux base, but would like to explore WHS as well)
-Will be able to authenticate with (full administrative rights) all machines in a Windows workgroup environment, and in a Mac OSX environment
-There will be plans for a mobile app

Is that even enough info for someone to point me in the right direction? I'm assuming it will be either Java or .NET(maybe?)

Thank you greatly in advance.