They should be providing the source under JDL or JRL license. With 1.1.3, the native acceleration is also available for amd64.
*sun-jai-bin-1.1.3 (03 Apr 2007) 03 Apr 2007; Miroslav Šulc <fordfrog@gentoo.org> +sun-jai-bin-1.1.3.ebuild: Version bump and migrated to Java generation-2 This was already done ages ago.