I just added source_receipt function thats in spk-ls into libpkg.sh. I also source libtaz.sh inside of libpkg.sh now. I hope this will not cause any problems since source_receipt in libpkg.sh made more since then in libspk.sh to me.
You can remove source_receipt function in spk-ls at your own pace now.
PS I think source_receipt could be used in cookutils and other tools also.