What is the relationship between the IPython notebook and Salvus?

I'm at a conference at Brown University this week with Fernando Perez (who started IPython), so I'm writing a short post about some of the relationships between IPython and Salvus. I'll hopefully post again later this week once I've had more time to talk with Fernando.  We are both giving talks about notebooks on Wednesday.

• The IPython Notebook is currently mainly aimed at single users running everything on their own computer, but Salvus is aimed in the exact opposite direction -- at tens of thousands of simultaneous users on a large cluster.
• There is currently no code overlap between the two projects, except that they depend on some of the same third party libraries (e.g., mathjax, codemirror, etc.). 
• The IPython notebook's backend is implemented using Tornado, but I implemented Salvus's using Node.js (for dynamic content) and Nginx (for static content).
• When I last checked, the IPython frontend is implemented in straight Javascript, whereas I'm implementing Salvus's frontend in CoffeeScript.  I had actually implemented the dynamic backend of Salvus using Tornado, but completely rewrote it because I needed better asynchronous database support and wanted to share more code between the client and server.
• IPython is BSD licensed open source code available right now and something anybody can very easily install on their own computer. In contrast, Salvus isn't available yet, and will (for now) only be available as a web app, since I designed it from the ground up to run on a distributed clusters.
• Ipython, Salvus, and the Sage notebook all have a similar feel, since they are were inspired by Mathematica's Notebook interface. I personally never used Mathematica notebooks, but a student of mine, Alex Clemesha, who did much early work on the Sage Notebook, was a big Mathematica user.
• At some point, I hope to use the infrastructure (hardware, virtual machine management, etc.) I've developed for Salvus to also make the IPython notebook available as part of Salvus.
• I'm designing Salvus mainly for using Sage, whereas IPython targets running pure Python and numpy/scipy code.
• With Salvus, I'm putting more work into worrying about compatibility with Android and iOS devices, since I use my iPad 3 and Nexus 4 a lot. E.g., for tab completions in Salvus, I rewrote the CodeMirror completions listing so it is usable on my phone (many standard things are almost usable.
• A huge amount of the work that went into the Sage Notebook over the years was to support embedded 2d and 3d graphics, interactive widgets and controls (the @interact decorator), debugger, integrated Cython support, mathematics typesetting (mathjax), etc. For Salvus, I consider having all this functionality a very high priority, though it is a daunting amount of work to implement. I don't know if interactive widgets (say) are a high priority for IPython, or even on their roadmap, but I'm sure I'll find out this week.   Incidentally, the analogue of interact for Salvus will be much better than what is in the Sage Notebook, since I've had tons of students and people ask me about fundamental shortcomings of interact over the years, and I'm addressing them from the ground up in the new implementation. 
• Salvus and Sage's underlying worksheet format is arbitrary HTML, whereas IPython's is Markdown. This has pros and cons.