I think the plan sounds great and would happily contribute to the effort, especially for the EtherCalc part. :-) Have you considered EtherPad Lite? It might be

I think the plan sounds great and would happily contribute to the effort, especially for the EtherCalc part. :-) Have you considered EtherPad Lite? It might be a more appealing choice than EtherPad, considering the common Node.js codebase.