It's hard to think that the answer to all of our platforms and languages is yet another platform and language.
Java set out to solve a very similar problem (write once, run everywhere) and the issues it ran into didn't involve the language itself but the platform specific framework/libraries.
Furthermore, let's remember that a developer can build C code on virtually all major operating systems using various compilers without being encumbered by licensing issues.
Therein is the fundamental difference. This isn't "write once, run everywhere". Nor is it a new platform. It is a method for bringing one code base to many platforms.
Java set out to solve a very similar problem (write once, run everywhere) and the issues it ran into didn't involve the language itself but the platform specific framework/libraries.
Furthermore, let's remember that a developer can build C code on virtually all major operating systems using various compilers without being encumbered by licensing issues.