relicense under GPL or add CLA

[maxadamo]

I noticed this issue, which was "discussed" and closed some time ago and I'd like to chime in: https://github.com/lepture/captcha/issues/6

There is nothing as reassuring as the GPL license, either for end users and for the contributors, because the GPL license guarantees that your contributions won't be sized by individuals or organisations. All the problems that we are seeing these days are caused by licenses being permissive in the wrong way.
We all know what happened with Hashicorp, Redis, CentOS and a few others (*), but we also know that there are ways to prevent these situations from happening:

1. use a GPLv3 license
2. if you feel that GPL may cause problems with plugins or libraries using different licenses, you can use LGPLv3
3. add a CLA beside your license. If you still disagree what I have written, CLA is the Contributor License Agreement, which is used by corporations and communities, like as Microsoft, Openstack, Puppetlabs and so on. CLA enables contributors to always provide a binding opinion, and as such, CLA is aimed to encourage contributions.

I provide you an example of a project where I have been involved. Puppetlabs was bought by Perforce. Perforce could not close the code, because they had a CLA, and in order to close the code, they needed an approval from all the contributors.

The concept is as simple as it seems: I don't get paid to contribute a project, and this is my guarantee that you are not trying to take advantage from my contribution. So please be fair with me.

(*) I go by memory and I think only Redis is BSD, but MIT and Apache licenses suffer from the same general problems (if they do not come with a CLA) !