Considering the concept of CSI as "Corporate Social Innovation is a strategy that combines a unique set of corporate assets (innovation capacities, marketing skills, managerial acumen, employee engagement, scale, etc.) in collaboration with the assets of other sectors to co-create breakthrough solutions to complex economic, social, and environmental issues that impact the sustainability of both business and society."(KISER, 2014) Some foundations develop social initiatives. Can we consider foundations as a corporate that fits the CSI concept?
I would say Foundations serve as one of the main vehicles for CSI (as you define/describe above). Refrain from calling a foundation a 'corporate' as it causes some confusion.
I concur with Christos that foundations act as vehicles to implement Corporate Social Inititiates and innovations. These foundations might be required to implement the CSI's with a limited scope as determined by the sponsor/donor or the constituting instruments but if they are not limited they would be well positioned to innovate from lessons learned and emerging issues from a dynamic environment and changing economic and social situations. I further posit that it would be an interesting study subject. On the issue of "corporate" i think some foundations adopt a corporate form in their legal status.
I also agree that foundations don't belong to the concept of "corporate" when discussing about CSI. Despite this they may reasonably considered within the set of actors enabling the emergence of CSI, that means within the Network for Social Innovation.
I'm trying to picture the dynamics of these kinds of networks... it isn't easy, since they change over the time (according to the life cycles of SI) and they usually involved different actors depending on the industry, as well as on the "nature" of social aim pursued by the firm