How to make light pass trough stuff in YafRay?

I have a scene where there is lightbulb and light source inside of it. But I can’t get the light come out of the lightbulb but it all gets blocked by the “glass” faces.

In Blenders internal rendering (without raytracing) the light passes trough the lightbulbs “glass” because I set it to make or receive no shadows.
Using internal raytracing it also works, but the shadows of characters are all too sharp, and it just doesn’t look as good as with YafRay.

I have figured out couple ways to “fake” the light (having the lamp outside of the lightbulb for one), but I would like to know if there is way to prevent material casting shadows in YafRay rendering?

Not sure if this is what you need, but unlike the built-in raytracer, for yafray glass materials one has to lower the opacity using the alpha slider in material float.