The Blend4Web team writes:
The year 2017 is coming to an end, so it is time to present the final release of this year. It brings several important new features, major inner refactorings and fixes for a number of issues. First of all, Blend4Web now supports Principled BSDF node that basically brings PBR materials to everyone. Next, we have overhauled engine's internals to meet ECMAScript 6 standard and made Blend4Web available through NPM (Node.js Package Manager). We’ve also improved support for Cycles nodes, physics engine and Fast Preview mode.