Note: This article applies to SQL license / purchasing requirements for DocuShare ONLY
This is complex question considering the various options of SQL Server (Enterprise Edition, Standard edition, etc) and if the SQL Server is 100% dedicated to DocuShare or being used by other users or apps. Microsoft offers various License options for SQL Server (CPU CAL, End User CAL, Device CAL) which the customer will need to understand and purchase according to his/her situation.
http://www.microsoft.com/sql/howtobuy
The "DocuShare Server application" by default Connects to the SQL Server 20 times as the same User (15 connections for JDBC, and 5 connections for Drala workflow). These settings can be reconfigured for a larger or smaller number of Database connections with the understanding that it would have an effect on performance (the default values are optimum). It is the customers decision which SQL Server Editions and Licensing option is best for them. If they are uncertain which option is best for them, they should contact Microsoft or their SQL Server reseller.