Hi Leon,
A few explanations - bare with me 🙂
In terms of "license types" all Autodesk Vault licensing is concurrent - this means we license Vault via a network licenses that set the maximum number of users permitted to access Vault at the same time. Furthermore users cannot mix Server and Client installations - this means that if your server is Autodesk Vault Professional, only Autodesk Vault Professional clients are able to connect (You cannot connect to a Professional server with Vault Basic clients).
In terms of external parties, from the Autodesk Vault lic agreement we make the following user definition:
For this product, “Personnel” in the License and Services Agreement shall mean Licensee’s individual employees and Licensee’s consultants, contractors, customers, agents and others with whom Licensee conducts business for whom Licensee has purchased a license to Licensed Materials who Access the Licensed Materials only for Licensee’s benefit or as part of Licensee’s project.
So, if desired you can purchase licenses and provide access to external parties via VPN or some other method, there are some further definitions around the licensing behavior and VPN in the EULA which may be worth reading through.
Note that for users requiring read only access to the data in your Vault - Autodesk Vault Professional does provide a read only web client that will allow access without consuming a license.
Finally - Autodesk does provide a lower cost license "Autodesk Vault Office" that permits non-CAD users read-write Web Client access to Vault Professional along with Microsoft Office (Word, Excel, Ppt) add-ins. It may be worthwhile speaking to your Autodesk Partner about this license for some of your users, as I mention this license does not give the user a full thick client but they can check out and check in single Office documents / pdf etc via a webclient.
Hope this helps.
Allan
Product Manager
Autodesk, Inc.