Are there any limits imposes by running with a Windows XP machine acting as the server?
Yes, Windows XP has a hard-coded limit of 10 network users. Since Blue Link needs to be able to read from at least the configuration file on the server to obtain the list of databases, the limit to the number of Blue Link users would therefore also be 10 assuming that you don’t use the Windows XP machine hosting Blue Link for ANYTHING ELSE. If that machine shares files or folders for other users or applications you may not be able to get to the 10th user in Blue Link.