Hmm, the terms for my CenturyLink fiber connection explicitly allow running servers (with some reasonable limitations): "Service may be used to host a server, personal or commercial, as long as such server is used pursuant to the terms and conditions of this Agreement applicable to Service and not for any malicious purposes. Malicious purposes include without limitation Spam, viruses, worms, Trojans, Denial of Service (DoS), etc."[1]

1: http://www.centurylink.com/legal/en/highspeedinternetsubscri...