line-3d.glsl

  vec3 point3D = mix(pointA.xyz, pointB.xyz, position.z);
  vec4 eyePos = modelViewMatrix * vec4(point3D, 1.0);
  float spriteWidth = uniformRadius * vertexRadius * (2.0 / 3.0);
  vec4 projCorner = projectionMatrix * vec4(
    0.5 * spriteWidth, 0.5 * spriteWidth, eyePos.z, eyePos.w
  );
  float computedRadius = projCorner.x / projCorner.w * screenWidth;

Fixed version below from @wwwtyro's example

        float cr = uniformRadius * vertexRadius * 2.0 * screenWidth / aspect;
        float wz0 = abs(cr / (modelViewMatrix * vec4(pointA.xyz, 1.0)).z);
        float wz1 = abs(cr / (modelViewMatrix * vec4(pointB.xyz, 1.0)).z);

        vec2 pt0 = screen0 + wz0 * (position.x * xBasis + position.y * yBasis);
        vec2 pt1 = screen1 + wz1 * (position.x * xBasis + position.y * yBasis);