TFS Basic is not a separate download.  It’s just a choice in the TFS configuration wizard.  So to get TFS Basic, you download the regular Team Foundation Server installation, either 32-bit or 64-bit (yes, TFS now supports 64-bit Windows natively), and then run setup.exe.  After the MSI (installation phase that more or less just copies files to your disk) is done, you’ll see the following dialog.  Choose Basic, and finish your TFS setup in record time!