It is my understanding that Ubuntu is closed source, this being the case I feel it should not be listed or if it is it should have the "closed source" tag.
I may be wrong and if I am please let me know.
f1nzo This is what I have found about it: https://code.launchpad.net/ubuntu
Ubuntu does have some closed source components (such as hardware drivers), but the code base is open source. It's impossible to have 100% open source software these days. You can find out more information here or here.