It seems there's a few rather overprotective uncapitalist viewpoints out there!
Once patents have lapsed, as they have many years ago for the standard and bedrock designs, anyone is free to make and sell a similar item. And existing makers take this into account when deciding to enter the market. (They too have done a bit of copying) I don't think Tilgear's new planes have any of the patented modifiactions developed by today's top makers.
In the UK we are also free to copy patented designs for our own use - it is only sales for profit that is illegal. (I believe this is not legal in the USA). I could for eg. legally knock up my own Woodrat or Routerboss for my own use, but not sell it for profit.