I like the look of Open Calais extremely, the automated provision of metadata (think tagging) is like the Nirvana of "knowledge management" web sites, which I worked on about ten years ago and in which I have always maintained an interest (though I would describe myself as an interested tinkerer with solutions rather than an expert of any kind, and I confess I have a very hard time with the concepts of the semantic web).
I try unofficially at work to keep an eye open on this kind of technology, and have a little test site which I play with for these purposes (I'm a big Drupal fan too by the way). I wanted to try installing Open Calais on this test site and try throwing a few pages of content at it to see what the results would be, however I got a bit nervous about doing so when I saw all the legalese attached to the request for registration key. Has anyone got some guidelines on this? Would it cause any problems for me just to play with it for a while?

Thanks for taking the trouble to reply, I will give Open Calais a whirl with interest and enthusiasm!
Hi Martin,
Thanks for your interest and yes - please feel free to test and experiment with OpenCalais. That's what it's here for.
The terms of service prohibit processing private, proprietary, confidential or sensitive materials, as we want to be clear -- we do NOT keep the content you submit, but we DO keep a copy of the metadata that we extract and send back to you.
OpenCalais is not a private service, and it is your responsibility to police the content that you submit. So take another look to make sure you are comfortable with our TOS, and the feel free to jump in.
See some ideas for what others are using OpenCalais to do in our gallery and in our blog - for instance, here's what some top publishers are using us for: http://www.opencalais.com/blogs/kristathomas/how-publishers-are-using-opencalais
To answer your 2nd question: OpenCalais is a strategic initiative from Thomson Reuters to support the interoperability of content across the digital landscape.
Our goal with this initiative is not to make money, but rather to make it easy for folks to categorize and tag their content in a uniform and consistent fashion that complies with Semantic Web standards.
Offering a de-facto standard for making content interoperable in this fashion ultimately benefits Thomson Reuters, as it enables us to track themes, memes and trends on the Web, and to potentially do things like link out to relevant content that helps provide context to our readers, customers and other constituents.
This vision for content interoperability gives us the freedom to offer our metadata generation service free of charge - up to 50,000 documents per day - which increasing load we support with scalable resources.
(Beyond that, we offer a very affordable licensing fee to bring users up to 100,000 documents per day - and on up from there for high-volume usage.)
As noted, the value exchange to us is in the metadata, in the growing body of interoperable content, and in the ability to support innovation, experimentation and the continued evolution of the Web.
We are fully committed to OpenCalais, and we offer the API for both commercial and non-commercial purposes precisely to inspire creativity and enterprise by a new wave of innovators and entrepreneurs.
There is no plan to someday "drop the other shoe" and charge folks for the basic service, full stop. Hope that helps, and let us know if you have any more questions.
-Krista
The OpenCalais initiative