The compile error using Java 5 on MacOS is:
(compiling rnrs/unicode.scm to kawa.lib.rnrs.unicode)
rnrs/unicode.scm:110:3: no known slot 'normalize' in java.lang.Object
rnrs/unicode.scm:110:39: no known slot 'NFD' in java.lang.Object
rnrs/unicode.scm:113:3: no known slot 'normalize' in java.lang.Object
rnrs/unicode.scm:113:39: no known slot 'NFKD' in java.lang.Object
rnrs/unicode.scm:116:3: no known slot 'normalize' in java.lang.Object
rnrs/unicode.scm:116:39: no known slot 'NFC' in java.lang.Object
rnrs/unicode.scm:119:3: no known slot 'normalize' in java.lang.Object
rnrs/unicode.scm:119:39: no known slot 'NFKC' in java.lang.Object
make[2]: *** [scm-classes.stamp] Error 255
make[1]: *** [all-recursive] Error 1
make: *** [all-recursive] Error 1