Open Source Authoring Tools

Can anyone provide me some info about the leading Open Source Authoring Tools available in the market? I’m having some other doubts too like Are these tools as good as the licensed options available, On which parameters should I compare these tools to know which one fulfills my requirements optimally and most importantly what about the ownership of the content; it stays with author or the content goes public?

Many good options exist in market like Adobe Captivate, Dominknow Claro, Camtasia, CMgroup Create, Gomo- Learning, iSpring Pro etc. Some of the Virtuous opensource and free alternatives can be what2learn, Xical, ClassTools, eXe, Wink …