If a Linux Distribution is under GPL, and I would redistribute it, is it correct that I only need to be able to give the sources? For example, say I build a 4-in-1 multi distribution DVD (I got sick of burning 4 separate discs so I made it multi-bootable). Could I distribute it for others to use without facing a lawsuit?
I read http://www.gnu.org/licenses/quick-guide-gplv3.html and interpret it as clearly saying that you need to include the sources:
Both versions of the GPL require you to provide all the source necessary to build the software, including supporting libraries, compilation scripts, and so on.
The same page also summarises the exceptions, i.e. cases in which you do not have to include sources.
Thus: if the distribution is under a current GPL version then you should include the sources when redistributing it and/or modifying it.