As Rob Caron wrote on his blog, the RTM version of Team Foundation Server can be downloaded from MSDN Subscriber Downloads. To be precise, you can download the Workgroup Edition and the Trial Edition. The Workgroup Edition is limited to 5 users. If you have more users that need to access a single TFS instance you need to purchase another edition of TFS like the Standard Edition. I cannot find a reseller in the Netherlands, but the list price in the USA is about $2.800.
In any case, you need a Client Access License (CAL) for accessing a Team Foundation Server. If you are a licensed user of one of the Team Editions of Visual Studio 2005, you already have a CAL and are ready to go. Team members without Visual Studio that want to connect from Excel or MS Project or want to view the Project Portal should buy a separate CAL. This would cost about $500.
This morning I upgraded my Release Candidate instance to the RTM Workgroup Edition. This only took about an hour and a half and went very smoothly. If we manage to buy a license for the Standard Edition, upgrading to the full version should be easy and will not require a reinstall.