Yes, I think so and I think Freemium is the way to go. If it’s crowdsourced then the free version has to feel like a complete product, as the contributors will most likely see it as the payoff of their work. If it’s outsourced then the free version can be a bit more limited.
The Free part
A website service. Your site must be online and you enter your webbadress into a textfield, click a button and the service will crawl through the site applying all the rules. It would have to limit itself to only the entered domain, but could also be limited to the number of levels it will follow links. If crowdsourcing was used then the service would probably not have the level limit.
The Premium part
If the website service is level-limited, then a subscription modell would unlock that limitation. Otherwise I think the most money can be made from plugins to various development tools that big corporations would use. Plugins to IDE’s, such as Visual Studio, so that webdevelopers can check for potential bugs as a part of the build-service or on command. And Plugins to deployment and/or build tools, such as TeamCity. Pricing could be lowered on larger builk orders, or cheaper for smaller teams that have less money.
A subscription model could be worked into this as well, as the rules need to be continously updated (like an anti-virus program) to be really usefull.
There could also be tiers within the pricing and functionality of the tools using the rules. Such as a Pro version that supports configuration of various parameters.