Those who look at the differences between Quake 3’s and Wolf:ET’s BSP format, look up previous replies.
Now, it has been more than 2 years when dabbling in this so here is a screenshot of map called Pilsner that has been rendered in browser by using WebGL.
This is with lightmaps disabled (due them being external in Wolf:ET) and shaders missing although shader parsing is there and works well with Quake 3 maps.
Note, there is problem with rendering big maps like Oasis or these kind and there seems to be error in parsing vertices that get processed in web worker. However, this does not happen with small maps like Pilsner.
The code can be found here - https://github.com/Genert/bsp-viewer
However, I have not added instructions for running it locally as game files are not public in repository thus making it impossible to run it. Perhaps will fix this.