Manuskript is a new open source writing platform currently under heavy development. But the screenshots look promising, offering a Scrivener-like look and what gets me excited: a storyline graph tool, for tracking throughlines.
If interested, take a look here – http://www.theologeek.ch/manuskript/
Note – I haven’t tried the downloads, as the product currently needs a lot of support code, but my thanks to Oliver for pointing it out to me.
