I don't own them, but (speaking as a reenactor), they are generally not regarded as being "historically correct"... on the other hand, in the "buckskinning" community, they are widely used. I have friends who love them... they are well made, durable and comfortable. Some other makers along these same lines are Arrow Moccasins and Poppen Moccasins. Of all of these, Arrow's "Ligonier" shoepack is a close approximation to a known museum piece.
If historical authenticity is any concern to you, there are other options (kits, video instructions, some online instructions, other individual makers, etc.). Authentic mocs will definitely not be as durable or comfortable. One document from the 18th century states that moccasins were a "respectable way of going barefoot". Again, if authenticity is your goal, there are regional considerations... Eastern, Western, etc.