Cross Platform Desktop Application - Windows+Mac+Linux

Three years later and Javascript is now also a strong contender in this debate.

There are multiple options within the space.

• https://electron.atom.io/
• https://github.com/nwjs/nw.js/

And others

Even Microsoft has shipped Visual Studio Code, the cross platform version of their development environment, which is written in Javascript.

What is the Visual Studio Code editor built on

The benefits include utilizing the many available web libraries, and building/using your web development skills.

This sounds like a job for Xojo or something similar: http://www.xojo.com

Mac, Windows, Linux builds with easy GUI design and native apps. Custom UI easily done also, and you'd then have one code base for all three platforms. You can download and use the software for free to develop and test, only requires a license once you decide to build your app.

You can also conside Livecode

Livecode: http://livecode.com For any platform except web, it is opensource and it includes mobile targets as well, if your code is flexible enough to not being C# or Java.

An option is to build the core logic in a compiled library using C# and GUI independence and then plug it to livecode, leaving the UI work for that tool.