What proprietary hardware? Okay, in the server the environment reporting chip is proprietary, but for the rest the important parts are industry-standard. Now the OS is tied to their hardware, but if your data formats are open you really don't have to care that much.
Data is important. Hardware and software comes and goes.
The hardware with the Apple logo on it. What else does OS X run on?
It's all temporary. Data formats come and go too. Data interchange problems are temporary. If there's enough need to interchange the data, it'll be taken care of in the software eventually.