The Institute for Science(selection) of Animals developed the strain in France. They have patented the technology, if you will.
This is now a large company group-consortium of DeKalb,Hendrix and others, you can google the company and have lots of reading.
The provide parent stock for hatcheries around the world.
Their selective breeding programs and improved genetics continues. Most, BUT NOT ALL, the sex links and production strains of commercial birds come from the breeding programs of these poultry genetics companies.
The I.S.A. is a licensed, patented line. Townline is the for sure, an approved hatchery. Others who claim they are? It is unknown.
Bottom line? the ISA is one awesome layer and has a fine personality and outstanding feed conversion ratio.