JOGL Hardware Shadow Mapping Transparent Shadow Texture

Question

I'm using hardware shadow mapping on JOGL based on the demo(HardwareShadowMapping) supplied by the distribution. After generating the shadow texture from lights point of view, I apply it to my scene with no problems.

What I'm looking for is soft shadows instead of pitch black shadows. Is there any way that I can change the alpha values while applying the shadow/depth texture? Btw I'm not an expert on OpenGL especially about custom shaders and I don't want to spend more time on understanding and developing custom shaders instead of the game.

Here's a screenshot of the application in case you come up with another solution to what I'm trying to achieve. The game is actually a hack&slash RTS hybrid.Here's the pseudo code of the gl event listener attached to shadow pbuffer.

  gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
  gl.glPolygonOffset(polygonOffsetFactor, polygonOffsetUnits);
  gl.glEnable(GL.GL_POLYGON_OFFSET_FILL);
  //render shadow casting geometry
  gl.glDisable(GL.GL_POLYGON_OFFSET_FILL);
  gl.glBindTexture(GL.GL_TEXTURE_2D, lightViewTextureID);
  gl.glCopyTexSubImage2D(GL.GL_TEXTURE_2D, 0, 0, 0, 0, 0, textureSize, textureSize);
  //I sense here a way of updating alpha values of this texture