The idea for Muse started with Shadowrun. I've had the idea for a set of tools including a combat manager, character and gear manager, and campaign manager for the Shadowrun ruleset for quite a while. However, there is a lot of content for Shadowrun, and it got intimidating really quickly.
So, when Catalyst released Eclipse Phase, I decided it was a good time to start building the same sorts of tools I had planned for Shadowrun. As of this writing, there is exactly one Eclipse Phase book - the core book.
That, I can handle. And thus, Muse was born.
I plan to make Muse as easy to use as possible. Once I start building features that require an account, I'll be taking advantage of open source technologies that will allow users to log in using their existing accotns - Google, Yahoo, Facebook, etc.
In addition, I'll be opening up the source code; Eclipse Phase is released under Creative Commons, so why not do the same for the tools associated with it?
For now, if you find errors or bugs, contact me via Twitter, and I'll get right on it.