The Project 2013 SDK download is updated. The conceptual, how-to, and reference documentation in the download closely matches the Project 2013 developer documentation online content published on MSDN.
The Project2013SDK.msi download file now installs properly on Windows 8 and Windows Server 2012.
The Project 2013 SDK download contains:
The top-level online landing page for the Project SDK is Project for developers (http://msdn.microsoft.com/project).
Want to try out Project 2013?
Unfortunately you linked to the SharePoint Server 2013 Client Components SDK PREVIEW. Here's the correct link:
We just found out that you STILL deploy test-signed assemblies in your SDK which cannot be used for production application development . When are you going to give us fully signed assemblies?
For example, please run "sn.exe -vf Microsoft.Office.Project.Server.Events.Receivers.dll" on the bits you ship in the SDK. Output: "Microsoft.Office.Project.Server.Events.Receivers.dll is a delay-signed or test-signed assembly"
 Yes, we know that we can activate verification skipping on our dev boxes, but we can't redist those assemblies.
The link to SharePoint Server 2013 Client Components SDK is fixed. For information about the attached REDIST.zip file, see the notes in the post above. The Project2013SDK.msi download file will be updated by about March 28.
Thanks for the update Jim!
One more question: Why is the Microsoft.Office.Project.Schema assembly not available for redistribution? It just contains lots of DataSets and doesn't have a lot of external dependencies (as Microsoft.Office.Project.Server.Events.Receivers and Microsoft.Office.Project.Server.Library do), so I don't see any reason to prohibit redistribution. Could you please shed some light on this?
Good question. The attached REDIST.zip file now includes the Microsoft.Office.Project.Schema.dll assembly.
Local event handlers: The Microsoft.Office.Project.Schema.dll is used for development of some local, full-trust event handlers that include a DataSet in the event arguments, such as the LookupTableEventReceiver.OnCreating event receiver. While the schema assembly is used for development, it is not necessary to redistribute it. Installation of an event handler on another machine requires only the compiled event handler assembly.
Remote event receivers are required for Project Online, and are developed with the CSOM. Although the CSOM itself does not use datasets, the event receivers still expose the same data in the event arguments -- such as the LookupTableEventReceiver.OnCreatingRemote event receiver.
Thanks for pointing out this omission. We originally (in the Project 2007 SDK) excluded the schema assembly for redistribution because we don't document it in the managed code reference, and developers generally had easy access to test servers where they could copy the schema assembly. Developers for Project Online might not have an on-prem instance of Project Server.
Wow, great answer! Thanks for the update, your helpful answers and timely response. Big thumbs up!!!