More a legal question than technical

Both versions of Codeigniter mean CI2 and CI3, right?

Their licenses are both open source license. You can redistribute CI with your work according to licenses.

CI2: http://www.codeigniter.com/userguide2/license.html
CI3: http://www.codeigniter.com/user_guide/license.html

Yes, both versions CI2 and CI3.

Thanks you for that.  I should have re-read the licenses.