Perhaps you're right, but at least it seems like OpenAI would like to join if/when invited. Judging from the press release it sounds like this partnership intend to invite non-corporate/non-profit members soon (and I think they'll loose a lot of credibility and support if they don't):

"Academics, non-profits, and specialists in policy and ethics will be invited to join the Board of the organization, named the Partnership on Artificial Intelligence to Benefit People and Society (Partnership on AI)." ... "There will be equal representation of corporate and non-corporate members on the board of this new organization"

http://www.partnershiponai.org/2016/09/industry-leaders-esta...