One of the outcomes of the LOD-LAM Summit was a draft document proposing a new way to assess the openness/usefulness of linked data for the LAM community. This is a work in progress, but is already provoking interesting debate on options as the authors try to create a shared strategy. 

The proposed classification system is described in detail on the International LOD-LAM Summit blog but to give you a sneak preview, here are the rankings:

★★★★ Public Domain (CC0 / ODC PDDL / Public Domain Mark)

★★★ Attribution License (CC-BY / ODC-BY) where the licensor considers linkbacks to meet the attribution requirement

★★ Attribution License (CC-BY / ODC-BY) with another form of attribution defined by the licensor

★ Attribution Share-Alike License (CC-BY-SA/ODC-ODbL)

The authors encourage discussion of this proposal as they work towards a final draft this summer, so please take a look and tell them what you think!