A Short Guide To Open-Source And Similar Licenses

IANAL, but afaik this is wrong: "The only catch is that the other project must also be released under the GPL."

You can use GPL-code freely in your own projects, but if you distribute, then it must be under GPL compatible terms. This is especially important in web applications and maybe other SaaS type solutions, where you don't actually distribute the software, but allow users to use it from your servers.

The Creative Commons "noncommercial" restriction being vague is quite important. A lot of content is being published under the CC licenses, and it would be good to get some clarification. For example, would an ad-supported re-publishing of the content be against the license?

Anyone know of authoritative definitions of this clause?

For reference here is a full list of OSI approved licenses: http://www.opensource.org/licenses/alphabetical