[astroalex]

One obvious difference I can see at a glance is that Maker.js doesn't support 3D models, while FluidCAD does. I assume Maker.js is a lower level library aimed at interfacing directly with CNC machines, while FluidCAD is focused on 3D design.

[WillAdams]

Maker.js is supposed to also support openjscad (or whatever they're call it these days, the JavaScript enabled version of OpenSCAD).