When using this CMS, are you allowed to remove the "Powered by Joomla", as shown in the demo: http://demo.joomla.org/demo15/ Or do you have to buy a license to do this?
No need to buy anything but i don't know if it's GPL license or Creative Commons Share Alike.....one I think it's GPL license ...then u can remove the powered by Joomla from pages free.....but befor edoing that read all the stuffs at http://www.gnu.org/copyleft/gpl.html Yes you can remove any thing from output(what is displayed in webpage) but inside source code u can not remove copy right informations(these copyright infos are within comments mainly) Confirmed from http://www.joomla.org/content/view/3510/1/ and http://www.joomlajunkie.com/f.a.q./frequently-asked-questions.html
yes, you can remove that from your footer. joomla is a gpl cms and you can do with it whatever you want