According to Umberto Eco, Goedsche in his novel Biarritz plagiarized Alexandre Dumas' Joseph Balsamo (as it says in the article) and Eugène Sue's Les mystères du peuple. But I think I've never heard that Goedsche directly borrowed from Joly. The common theory is that the motif of the conspirators' secret meeting on a cemetary (which Goedsche took from Dumas and Sue), after having been published independently from the rest of Goedsche's novel, was merged with material from Joly's satire to create the infamous Protocols.   

 Weblinks 

I removed the first weblink, as it leads to a personal blog which (despite its title) contains nothing about Goedsche/Retcliffe whatsoever.