Steve
Mostly Harmless
http://en.wikipedia.org/wiki/Lists_of_English_loanwords_by_country_or_language_of_originSee, now that's where I argue the point....
"Jujutsu" (and it's resultant variants) are not English words, nor Portuguese, nor anything but Japanese. The idea of it being a loanword, or transplanted term don't change the way it should be spelt. Both these concepts imply the word is borrowed from the original language (in this case Japanese), not that it becomes a part of the recieving language (English). And in that regard, it remains a Japanese word, no matter how many cultures and languages bring it into their lexicon.
As to the root languages changing the way that things are spelt, yes, that is the way it happens... when a language is formed from base, or root, languages. In English's case, that root comes from Latin (which is where "pader" comes from, and was a root language for much of European language forms), Germanic, Norse, and a few others. But none of it comes from Asian languages. What has happened is that certain Asian terms, phrases, and words have made their way into popular vocabulary. That does not make them English, though, any more than the use of "au revoir", or "ciao" make those words and phrases English, instead of French or Italian... and there the same common root language is present.
If "Jujutsu" was an English word, it would most likely be spelt "W R E S T L I N G", or "G R A P P L I N G". But it isn't, and shouldn't be treated as one, no matter how common it may seem.
Many... most... almost all of them are spelled differently than the root. Some are modified in minor ways, such as the removal of an accent. Others are modified in more prominent ways.
But, what I'm really suggesting is that in the context of Brazilian Jiu Jitsu, jiu jitsu is no longer a Japanese word at all. It is a Portuguese word derived from a Japanese root. It refers to a specific form of grappling, just as distinct as Greco Roman, Freestyle, Catch as Catch Can or Judo.