Can I, without permission of anybody, relicense some software from MIT/BSD license to GPL license legally? For example, may I take the Google Chrome web browser and re-release it under the GPL (under another name)?
It is just "what if" question. I will not do this, I promise.
Basically Yes - see http://www.fsf.org/licensing/licenses/index%5Fhtml
In case there are any hair splitting pedants on this site (really!) there isn't really any such thing as the MIT license - see above link.
The only difference between the 'MIT' license and the BSD license is that some versions of the BSD license had had restrictions on using the name of the institution, others required you to advertise this!
In modern version (the two clause) this has all been sorted out.
For a simpler introduction see http://en.wikipedia.org/wiki/Mit%5Flicense
edit. As Daniel syas - you can't relicense code you didn't write (or weren't granted the right to do) however you can REDISTRIBUTE 'MIT' code under the GPL which is probably what you are actualy asking.
You can't re-license without the copyright owner's permission, if there is one. As pointed by ceejayoz, some licenses allow that, but most of them do not.
What you can do is license your additions/modifications in a different, possibly more, but mostly always not lesser restrictive wording.
I use the OSI as the reference site and there find:
http://www.opensource.org/licenses/alphabetical
which points to:
http://www.opensource.org/licenses/mit-license.php
which starts:
Open Source Initiative OSI - The MIT License:Licensing [OSI Approved License]
The MIT License
Copyright (c)
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
I believe you can redistribute or relicense as you suggest. The Wiki says:
http://ideas.opensource.org/wiki/help/license
: Can I freely include code in my project that is under a compatible license? ¶
Not necessarily. Compatibility just means that you can create code that derives from both. However the combined result must respect both sets of copyright terms. Therefore including code under another license may require you to change your own license terms.
In general projects that use a permissive license (such as the MIT license) need to be careful when including other code, but their original code can be widely reused. Conversely projects that use a restrictive license (such as the GPL) can often safely use code from other projects, but their code cannot be reused as widely. This directionality can be a source of conflict between different developers and projects.
The relevant line in the MIT license is:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
Therefore, while you can certainly include MIT licensed code alongside of GPL licensed code, the MIT license is "sticky". Any attempt to dual license the code with GPL would have no effect, because the MIT license allows anyone to ignore the obligations of the GPL. If you removed the MIT license notice and inserted the GPL you would be in violation of the MIT license.