... and still write in English?

There are a lot of similarities between the Potter stories and Lord of the Rings (as, of course, there are a lot of similarities between Star Wars and Lord of the Rings, but nobody is suing George Lucas)...
- a wise old wizard with a long white beard and pointed hat
- a young fellow burdened with having to battle "the dark side"
- a villain whose name people don't like to say
- temptation of the young hero to join the dark side
- magical artifacts passed on from old to young
etc

And Tolkein borrowed from much older myths, etc.

If "Larry Potter" had been as entertaining and well written as "Harry Potter", it would have done well on it's own.