Microsoft Mathematics Replacement

I'm a big fan of Microsoft Mathematics. It's got an ideal combination of a command line and a skeumorphic interface that resembles the sort of calculator I used back in high school. Whenever I have any reasonable math question that needs answering, I can launch the program and quickly get an answer. I don't need to be internet connected either, it's locally downloaded and starts up instantaneously. It does what I need it to and gets out of the way.

Unfortunately the program is growing long in the tooth. The latest downloadable version, 4.0, released in 2011 and I don't even think it's available on Microsoft's website anymore. This leaves me really concerned as to the future accessibility of it and its ability to run on future operating systems. This is frustrating because Microsoft Mathematics is a really, really good program. Is there any replacement for it that's actively maintained? I've never seen anything else that's quite like it.

Alternatively, if anyone from Microsoft is reading this...please resurrect Mathematics as a simple downloadable program! It doesn't really need any enhancements. Just a promise of maintenance so it will continue to run in the future!