I am having a little bit of trouble understanding the status of this project at this point.
Would it be possible to get a summary of where you are at or possibly update the OP to reflect whatever is currently happening?
I'd like to get involved but I am finding it difficult to follow this thread.
I will try to provide a more detailed answer soon.
In brief:
Lots has changed since this thread's creation. The original design for Sia was fundamentally broken in several severe ways and many things had to be reconstructed. Original estimates had Sia being released something like June or August of 2014. As Sia is not released and it's almost a year later, those estimates were clearly mistaken.
Today we have a beta that (sorta) works, and a blockchain that's (sorta) tested. All of the features have been nailed down and finalized, and 95% of them have been implemented. All that remains is to remove the (sorta), which I expect will take about 6 weeks. We're planning on releasing another version of the beta in about 2 weeks that has a bunch of bugfixes. I'd still say that it works (sorta) well, there are a handful of problems that remain. We know how to fix most/all of them, we just need to put in the hours.
At release, you'll be able to mine for coins, rent out your hard drive, and upload files to the network. Files will be encrypted client-side. You will be able to share files using a '.sia', which is the decentralized version of a '.torrent'. It tells your program how to download a larger file from the Sia network.
For developers: there will be a documented API on how to use Sia. It's entirely possible to build separate applications such as a 'decentralized YouTube' on top of Sia. At release, we will have very little information on how to build applications that use Sia, but the API should help. We do intend to focus more on developers once the currency has launched.