Q:

Windows Licensing Question

This is slightly off topic of programming but still has to do with my programming project.  I'm writing an app that uses a custom proxy server.  I would like to write the server in C# since it would be easier to write and maintain, but I am concerned about the licensing cost of Windows Server + CALS vs a Linux server (obviously, no CALS).  There could potentially be many client sites with their own server and 200-500 users at each site.  
The proxy will work similar to a content filter.  Take returning web pages, process based on the content, and either return the webpage, or redirect to a page on another webserver.  There will not be any use of SQL server, user authentication, etc.  
Will I need Cals for this?  If so, about how much would it cost to setup a Windows Server with proper licensing (per server, in USA)?  

A:

This really is an OT question. In any case, there is nothing easier than contacting your local MS distributor. As stackoverflow is by nature an international site, asking a question like that, where the answer is most likely to vary by location (MS license prices really are highly variable and country-specific) is in my opinion not likely to receive an useful answer.

A:

I realize this isn't exactly answering your question but if you want to use Linux, maybe you want to look into using Mono.  .Net on Linux. 

A:

If users will not be actually connecting to any MS server apps (such as Exchange, SQL Server, etc) and won't be using any OS features directly (i.e. connecting to UNC paths) then all that should be required is the server license for the machine to run the OS. You need Windows Server CALs when clients connect to shares, Exchange CALs for mail clients, and SQL Server CALs for apps that connect to your databases. If the clients of your server won't be connecting to anything but the ports offered by your service, you should be in the clear, and it shouldn't cost any more to build a server for 100 users than 10.

