Microsoft has released the SharePoint Foundation 2010 Client Object Model Redistributable. The assemblies for the .NET and Silverlight versions of the SharePoint client object model are included.
The installer deploys these to the C:Program FilesCommon FilesMicrosoft SharedSharePoint Client folder of the development computer. (They are 64-bit.) In addition, resource assemblies are deployed to a subfolder named with the culture ID.
The assemblies for the .NET version must be included when you distribute solutions that target them. SharePoint client assemblies obtained in other ways cannot be legally redistributed.
You may distribute the assemblies for the Silverlight version along with a solution that targets them. They can be encased inside the Silverlight xap file. Alternatively, your solution can reference the Microsoft.SharePoint.Client.xap located on every SharePoint server in the SharePoint root: ...14TEMPLATELAYOUTSClientBin folder. It is also possible to cache the Silverlight assemblies. They are located in that same folder.