This is Kyoto Cabinet, the successor to Tokyo Cabinet. It's a database
engine. It's not a drop-in replacement for Tokyo Cabinet; the two packages
can coexist without a problem. However, the developers recommend using
Kyoto Cabinet whenever possible.
It has no OS version restrictions of which I am aware; it builds fine as UID
nobody in maintainer mode on 10.6 x86_64.
It should go in the "libs" section, like tokyocabinet and tokyocabinet9.
I note that the existing tokyocabinet and tokyocabinet9 packages have
BuildDependsOnly set to True, without a note in DescPackaging. It's not
clear to me why this was set this way, but I figure it's probably for a good
reason, so I did the same in my kyotocabinet15 package.