Can DNA act as a translation substrate?
As far as I can tell from the paper you linked to (Damiana et al) it is possible but inefficient:


  Naturally, we tried to translate ssDNA, but as previously described
  elsewhere, direct DNA translation was not really efficient in absence
  of antibiotics such as neomycin [5] and [6]. It seemed that the
  elongation phase was the limiting step in the direct translation of
  single-stranded DNA. Whether direct participation of DNA in protein
  synthesis could play any role in vivo must be excluded, although such
  a role could be attractive for modelling the evolution of the earliest
  forms of life.