I can't see any information about the translation though.
Who did it?
Was it published?
Is it in the public domain?
Their main page doesn't say anything (that I can see) as regard to the translation itself.
edit: is it just Walther Sell himself?
the copyright at the bottom writes:
© copyright 2009 - 2017 Walther Sell
and there is a new abridged version
edited by Walther Sell