Yes. It has spread. And was very non-virulent. And they got valuable data on what to do when H5N1 does become transmissible in Humans. However, had this Virus

Yes. It has spread. And was very non-virulent. And they got valuable data on what to do when H5N1 does become transmissible in Humans. However, had this Virus escaped, it would have fizzled. Showing airborne transmission does not mean the Virus would spread among ferrets and Humans under normal conditions. Mammalian H5N1 viruses might have already existed but failed to survive subsequent passage and thus did not evolve to become transmissible enough. Such lab experiments only add a minuscule risk to the much bigger risk of such a Virus occurring naturally.