Bob Marley would be totally irie, mon ... with his half-bro making huge money off Bob's name and likeness -- at least according to the brother's new lawsuit against Bob's estate.

Bob's widow and several of his children sued Richard Booker for trademark infringement last month ... claiming Booker was selling everything under the sun -- food, booze,concerts, and more -- by slapping the Marley name on the products.

Now, Booker -- who had the same mother as the late reggae superstar -- filed a countersuit against 56 Hope Road Music ... the company controlling Bob's estate.

In the documents, Booker says he's using the family name "with the consent, authorization and by the instruction" ... of Bob and their mom, Cedella. 

Booker wants the court to throw out the estate's lawsuit against him -- and give him the all-clear on continued use of the Marley name.