Ubuntu MOTU folks seemed to have expressed that they don't want a bunch of ruby packages to maintain because they are short-handed. It appears that the Ubuntu Way is to make MOTU the 'maintainer' for all packages in Universe, whereas debian defaults to having individuals as maintainers although it sometimes has teams too.
Thom's been active in helping getting packages into debian, and two people have offered to help get them from the debian new repo into ubuntu since the package freeze is coming up soon for ubuntu 9.04
libjson-ruby – in both debian etch and ubuntu intrepid
libextlib-ruby – I've built this package and its in debian new.
As soon as we get a tagged version of ohai we are ready to build an ohai package.