A PCB consists of multiple layers, each one of which is described by a gerber file. gerber-to-svg renders each individual layer to svg; this project aggregates all the layers and stacks them up (hence the name) in the proper order.
We use gerber-to-svg (it is the best we've ever worked with) server-side, but we use svg-stacker to generate images for the cases where we need them (thumbnails, printouts, etc.)
On the front-end, we use html5 canvas rather than a pre-stacked SVG.
This is true, though there is a workaround by using cdn.saw fit.com domain. I use the trick to display SVG figures in these white paper notes[1], and I found out about it in this issue thread[2]
This is only a Gerber file renderer. Gerber files only contain manufacturing data (it's basically a vector image format).
So 3D models would be very hard to add. It would only work if you export a BOM with position data and references to STEP files for your board. This is not currently supported by most commercial software (no idea if it's possible with KiCad), positions are easy to get, but then you'd still need the 3D models (including position offsets and rotation).
Does anyone knows how this compares to Gerber-to-svg? https://github.com/mcous/gerber-to-svg