All articles in the wiki section of k2g2 are licensed under the creative commons share-alike license.
This means, that you can freely reuse articles for any purpose as long as you credit to the original authors. If you decide to modify content from k2g2, you must release it under the very same license.
For other content on k2g2, such as blog-entries, images, patterns etc. the respective authors may chose from a variety of licenses. Where no license has been declared, the copyright remains with the original author.