You may not think about it, but content filtering is a security issue! Filtering out pornography is a major enforcement aid for many businesses and public institutions which do not allow access to such material from their network. It is therefor interesting from a security standpoint that tools exist to facilitate the control and filtering of pornography, violence, and racist content, and that such control can be extended over a variety of languages.
Ubuntu Linux has had suggestions to implement such things in their IdeaPool. I took that basis and Dan's Guardian and extended out the idea into a suitable set of information for easily and effectively deploying such a thing. Although these should not be enabled by default, they should be available for parents, schools, libraries, businesses, and government institutions which may want or even be legally required to prevent access to such content.
I have also made a post about this on the Ubuntu Linux development list. The post is accessable via gmane, and thus you can get in on the conversation by clicking Action->Followup and posting. If you are using or considering using Ubuntu, this would be a good way to influence its development.
I have said that this is a policy enforcement tool. I do not advocate blind censorship, nor do I believe that we should enable these tools by default. However, I believe that any serious Linux distribution should present a set of important features to the user. To any user, a Web browser, e-mail client, music player, and friendly desktop environment are important. In many situations, content filtering would also be an important feature to be available; however, it would also be a bad feature to enable by default, as many users will not want it.
Parents with young children have a responsibility to actually raise their children. Dan's Guardian could be configured to block access to sites determined to be inappropriate based on a given set of rules. The parents could decide to block "pornography," "violence," and "racism," or any combination thereof. They could also decide to monitor their children themselves and have Dan's Guardian simply log access and allow it; or deny and log access. Most parents wish to prevent their children from accessing certain content, and so having an available content filter would be a great deciding factor.
Businesses and public institutions also have a legal responsibility to content filter. A business, a school, or a library can be fined or even sued if by their negligence certain content is accessable in many situations. Such institutions could look to a content filter as a solid, free, and flexible best effort both to enforce policy and protect them from legal troubles.
In any case, Dan's Guardian can be combined with Clam Anti-Virus to filter out viruses, worms, trojans, and other malware. Such malware may come inside infected executables or embedded into corrupted content that exploits browser and support library bugs. This would be of interest to many users and institutions.
With some work, it's possible to deploy these systems in such a way that they hijack unencrypted HTTP connections, both originating from the local host and being routed from the internal network. This provides zero-configuration proxying which would allow a clean and solid policy enforcement solution regardless of the lack of administrative control over other network nodes, such as laptops with custom operating systems, or LiveCDs. This also allows the virus protection filtering to be highly effective, allowing unconfigured Windows machines using an Ubuntu gateway to be automatically protected from malicious Web sites.
Although I am against censorship, I believe that this would be a great policy enforcement tool to have available, but disabled by default. It would only be a problem if ISPs decided that their policy included mandatory filtering; in such cases, the ISPs could easily run a low-budget project to deploy a proprietary content filter which the user could not disable. Thus, there should be no moral or rights issues harmed by the inclusion of content filtering software.