Arrangement: probably. I don't know too much about that event so I'm not entirely sure he put it together completely by himself, but it seems pretty likely to me. Booklet of course isn't really any help about that either.
Performance: depends on if Koshiro actually played any parts live during the set, maybe? We usually restrict performers to instrumental performances (we don't credit conductors as performers, for example), so if anyone is actually interested in minutiae, I guess we could discuss to what extent DJing constitutes an instrumental performance. Every DJ is different in how much of a set is prepared beforehand and what's mixed/transitioned/etc. live, scratching, all that jazz, so I'm not sure there's an easy answer there.
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