How many and what type of licenses do you need?

See our research below:

Microsoft claims that a "User" CAL will allow a single user to access the server from multiple devices:

Q. What is the difference between device client access licenses (CALs) and user CALs?

A. A device CAL allows any number of users to gain access to licensed server software from a particular device. A user CAL allows a particular user to gain access to licensed server software from any number of devices. In other words, a user CAL covers a particular user's access to the server software from work computers and laptops, as well as from home computers, handheld computers, Internet kiosks, and other devices. A device CAL covers multiple users' access to server software from a single, shared device.

From: http://www.microsoft.com/sql/howtobuy/faq.asp

In this same document it states that it would be more cost-effective in our environment if we purchase a Server plus User CALs:

Q. Which is better—the Server plus device CAL, the Server plus user CAL, or the Processor license?

A. It depends on the specific situation, but there are some general guidelines:

For externally focused server applications. Processor licensing is the obvious choice for externally focused server applications, such as Internet and extranet scenarios. Typically, counting devices or users in these scenarios ranges from difficult to impossible, so hardware–based pricing is more straightforward.
For mixed-use servers. For mixed-use servers that will be accessed from both inside and outside the organization's firewall, Processor licensing is generally favorable. Because the Processor licenses are probably needed for external users, there would be no need to purchase access separately for internal users through CALs.
For environments inside the firewall. For environments inside the firewall where client–to–server processor ratios are low, the Server plus device CAL licensing model will likely be the more cost–effective choice if there are multiple users per device (for example, in a call center), while the Server plus user CAL licensing model will likely be more cost–effective if there are multiple devices per user. For environments inside the firewall where client–to–server processor ratios are high, the Processor licensing model will likely be more cost–effective.

If you have a single user (login) to SQL Server 2000 (for example the login will be the user name "lawson") and you have multiple "devices" that will connect using this user we only need a single user to access the database. Since the standard purchase of the software comes with 5 User CALs that would be the best choice (since the user "sa" will also need connect to the database for administration tasks the few extra CALs will be needed).

In the event that we set the User CALs to 5 and Lawson does not work properly and it is because of the number of User CALs we can increase this number during our testing while additional CALs are purchased. Microsoft states that: "SQL Server installations that are part of your day-to-day operations require production licenses."

From: http://www.microsoft.com/sql/howtobuy/default.asp.

Since this new server will not be "day-to-day" until after we migrate to it we are within the guidelines of what is expected by Microsoft. The license manager within Microsoft SQL Server will allow you to set the number of CALs to any number and "expects" that at some point when this is a "day-to-day" system you will have purchased all the required licenses.

So to sum it up. You only need the Server plus 5 User CALs.