Peter,
I don't know if you got an answer to this yet.
I believe you can use VS 2005 Pro. However, you would still have to install
the Team Explorer to access Team Foundation Server. You will also need a
separate CAL for each developer.
VS 2005 Team editions all come with a Team Foundation CAL included.
DJ
> We have a relatively small number of developers in our group and would like
> to move to the team foundation server as an alternative to SourceSafe. My
> question is this: will we have to upgrade all our developers from VS 2005 Pro
> to VS Team Edition for Software Developers in order to use team foundation
> server?
If you want the full experience, you need one of the Team System SKUs. If
you merely wish them to be able to log in and check in and out source code,
you can accomplish this with Pro or greater and the client install for TFS.
This is the same way project managers, et al, get into the repository.

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Gregory A. Beamer
MVP, MCP: +I, SE, SD, DBA
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> We have a relatively small number of developers in our group and would
> like
[quoted text clipped - 3 lines]
> to VS Team Edition for Software Developers in order to use team foundation
> server?