Wow, now where TeamPlain Web Access is free for all TFS customers [1] you need to 'upgrade' your license to the unlimited license.
The creators - DevBiz - describe the process (which is as easy as downloading a ZIP file and placing it to a specific directory) in their blog at [2].
Enjoy! :-)
-Neno
P.S. BTW: If you've bought TeamPlain Web Access within the past 30 days before the Microsoft you can reclaim the money, but you need to do it asap since it is only a short time offer (see [1]).
[1] http://blogs.msdn.com/bharry/archive/2007/04/02/update-on-devbiz-acquisition.aspx
[2] http://dev.devbiz.com/blogs/teamplain/archive/2007/03/28/unlimited.aspx