Here's an article which pretty much sums up everything that I've seen and read on the issue so far...
The DLV (and the general public here) is impressed with his effort, but the DLV aren't confident they can let him loose in international competitions with his current prosthetic without this causing more problems in the future.
It seems that the biggest issue is what kind of prosthetic is needed for disabled athletes to compete in regular elite competition (like Pistorius), ie.) how stiff should a prosthetic be to replicate human legs? (and there are surely more questions to consider as well).
Rehm was only allowed to compete at the German Chamsps with special permission from the DLV, under normal circumstances he wouldn't have participated. Although they are happy with his performance, they are worried about the position this has put them in.