It’s assumed that your contribution will be licensed with the current license (generally). Maintainers can change the license but that wouldn’t affect prior contributions. Basically anything up to that license change would still have the original license. This is what makes forks possible when popular software changes their license.
In order to go back in history and change a license, you need either the consent of your contributors or a document that would grant you the power to do that. A CLA could (but not all CLAs will) grant a maintainer to change a license at will back in time.
Other famous software that has seen a license change: Redis and Terraform. In those cases the license changed but already released software is still available with the old license and that old license allows for forks.
You can incorporate MIT/BSD code in a proprietary project, but that imported code itself remains BSD/MIT licensed. For many projects, this is a technicality, but no, you can't claim copyright on MIT/BSD code that isn't yours.
But also nothing preventing you from doing it.
MIT can be relicensed, for sure.
The MIT license is not very long, and it contains this sentence:
> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
Which clearly state that you can't remove that license to put your own.
Probably the sublicense wording that many techies confuse with relicensing.
Also sloppy wording in discussions like HN where "relicense" is sometimes used as a shortcut for "combined with a compatibly-licensed work in a larger work that can be used under the whole-work license".
That is not the case with other licenses.
> 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:
> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
Note the "deal in the Software without restriction" and "sublicense" permissions and the virality of the terms that require the permission notice must be included with all copies.
One problem with this however is if someone has removed the license from the software like what has happened here, then that software really has no license because the license doesn't specifically state that it applies to derivatives. The Apache 2.0 license is much clearer on that subject of derivative works.
https://github.com/material-theme/vsc-material-theme/commits...
I'm not sure why the initial commit already says "official", but that's almost a decade ago.
https://github.com/material-theme/vsc-material-theme/commit/...