If you keep the traffic fairly low to the server you should be o/k. No commercial traffic/no porn. There are no restrictions for servers on their Business Class Service. Instead of using two modems and paying twice as much as you are paying now (some areas wont even do this) you can use a router and port forward the IP address of the server.
For anyone who's wondering the same question, here's a excerpt from the Acceptable Use Policy:
• access any other person's computer or computer system, network, software, or data without his or her knowledge and consent; breach the security of another user or system; or attempt to circumvent the user authentication or security of any host, network, or account. This includes, but is not limited to, accessing data not intended for you, logging into or making use of a server or account you are not expressly authorized to access, or probing the security of other hosts, networks, or accounts without express permission to do so; • use or distribute tools or devices designed or used for compromising security or whose use is otherwise unauthorized, such as password guessing programs, decoders, password gatherers, keystroke loggers, analyzers, cracking tools, packet sniffers, encryption circumvention devices, or Trojan Horse programs. Unauthorized port scanning is strictly prohibited; • copy, distribute, or sublicense any proprietary software provided in connection with the Service by Comcast or any third party, except that you may make one copy of each software program for back-up purposes only; • distribute programs that make unauthorized changes to software (cracks); • use or run dedicated, stand-alone equipment or servers from the Premises that provide network content or any other services to anyone outside of your Premises local area network (“Premises LAN”), also commonly referred to as public services or servers. Examples of prohibited equipment and servers include, but are not limited to, e-mail, Web hosting, file sharing, and proxy services and servers; • use or run programs from the Premises that provide network content or any other services to anyone outside of your Premises LAN, except for personal and non-commercial residential use; • service, alter, modify, or tamper with the Comcast Equipment or Service or permit any other person to do the same who is not authorized by Comcast; Network and usage restrictions • restrict, inhibit, or otherwise interfere with the ability of any other person, regardless of intent, purpose or knowledge, to use or enjoy the Service (except for tools for safety and security functions such as parental controls, for example), including, without limitation, posting or transmitting any information or software which contains a worm, virus, or other harmful feature, or generating levels of traffic sufficient to impede others' ability to use, send, or retrieve information; • restrict, inhibit, interfere with, or otherwise disrupt or cause a performance degradation, regardless of intent, purpose or knowledge, to the Service or any Comcast (or Comcast supplier) host, server, backbone network, node or service, or otherwise cause a performance degradation to any Comcast (or Comcast supplier) facilities used to deliver the Service; • resell the Service or otherwise make available to anyone outside the Premises the ability to use the Service (for example, through wi-fi or other methods of networking), in whole or in part, directly or indirectly. The Service is for personal and non-commercial residential use only and you agree not to use the Service for operation as an Internet service provider or for any business enterprise or purpose (whether or not for profit); • connect the Comcast Equipment to any computer outside of your Premises; • interfere with computer networking or telecommunications service to any user, host or network, including, without limitation, denial of service attacks, flooding of a network, overloading a service, improper seizing and abusing operator privileges, and attempts to “crash” a host; and • accessing and using the Service with anything other than a dynamic Internet Protocol (“IP”) address that adheres to the dynamic host configuration protocol (“DHCP”). You may not configure the Service or any related equipment to access or use a static IP address or use any protocol other than DHCP unless you are subject to a Service plan that expressly permits you to do so.
PLEASE READ the CC TOS before "running a server"......FWIW....your particular "use" seems to fall into the "Ummm...OK...just take it easy" category, from what I've pieced together from others who've done this....