Outlook 2000 for Exchange 5.5

We have an older Exch5.5 install that came with the Outlook 97 and Exchange client included. I noticed that some of the more recent packs include the Outlook 2000 client (at least for SBS editions). Does anyone know what the licensing method is for the 2000 client? Is it free to use as long as you have Exchange 5.5 installed? Where can I get a copy? Thanks.