When we use UFraw or other programs based on DCRAW we get the original picture, not the edited one.
When our photograffer takes a picture in DNG. Afterwards edits on this picture are done with photoshop or Lightroom. Picture is saved again in DNG.
When I open the picture the new picture in UFRaw I see the original picture.
How can I avoid this
You cannot. The edits in Lightroom are not done on the source image but saved as editing steps in the XMP (non-destructive editing). You could read the XMP-data but it won't help you, since you cannot re-apply the LR editing steps.
If you want to work on the edited picture, you will have to ask your photographer to export a TIFF from LR and use that instead of the DNG.
DNGs can contain a full size JPEG version of the image showing the adjustments. Not all DNGs have this, as it optional. It is possible to extract the preview from the DNG if it exists. This is clearly outlined in the DNG spec.
Note that even if a preview does exist, it does not necessarily reflect the current state of the image settings, since updating the embedded preview is also optional.
