Not just the models, Kicad uses Open Cascade for dealing with STEP files and probably some other things.
If you want a simple CAD tool for designing 3D part packages, I can recommend Solvespace. A lot of people find it easier than FreeCAD for smaller designs - like electronic components:
It can create step files for KiCAD, but can not read them. Some day I'd like to bring the step reader from gcad3d (or other) onboard so we can at least link them into assemblies. That'd be a huge integration project, but it's way smaller than OCCT.
>> The last time I looked, Solvespace has a rather simplistic way of generating STEP files, I don't think it would be easy to add reading them as well.
My short list (of big items) includes fixing the STEP output so they are recognized as closed shells when read by more tools. Someone has already proved the concept.
Reading step is hard, but the reader in gcad3d is plain C and does a decent job. It's also the same license. The real issue is that step is huge and includes things that cannot be represented in the Solvespace NURBS kernel. We will need to skip those elements. The even bigger job is implementing proper hierarchical models, and that should be done IMHO with an eye on supporting some more step features.
But it works for making KiCAD parts today. We also support linking IDF boards (.emn) into assemblies now, sans parts.
The Solvespace project might like to look at joining CAX-IF [1], there are recommended practice documents and testcases that may make interoperability easier.
If you want a simple CAD tool for designing 3D part packages, I can recommend Solvespace. A lot of people find it easier than FreeCAD for smaller designs - like electronic components:
https://solvespace.com/index.pl
It can create step files for KiCAD, but can not read them. Some day I'd like to bring the step reader from gcad3d (or other) onboard so we can at least link them into assemblies. That'd be a huge integration project, but it's way smaller than OCCT.