I am not a lawyer. You should get one, if you are concerned about possible legal issues.
You have to include a copyright notice (a ‘manifesto’, if you will) to each file that contains your work.
That ‘manifesto’ shall consist of:
Copyright © <years> <owner>.
<years> are years when this very file was created and substantially modified; you’ve said that you did not work on the project for a long time, so it might look like
2008, 2015 for example; do not use range (
2008–2015) unless the file was modified every year.
<owner> is who holds exclusive rights on this very file. The authors are owners if they did not transfer rights to someone else. An employee typically transfer his copyright on the work his paid for to an employer by terms of contract or (in many countries) by the law. So if you was working on the project during your work hours, you would better check that your employer does not claim copyright on it.
Either ⓐ the full text of a license in the case of short permissive licenses, e. g.: BSD licenses (2 clause, 3 clause), X11, Expat, zlib licenses; or ⓑ something that refers to the full text: Apache License v2 (see under APPENDIX), GNU licenses (see under ‘How to apply...’ in the GNU GPL) and other long and well-written free/libre licenses; also WTFPL :-), which is a sort of parody on complicated copyright licenses.
When ⓑ you have to put the full legal text of a license in the file
LICENSE in the root of code repository usually; when ⓐ this in optional and does not make any sense from a legal point of view, but often considered a good habit since it helps to detect the license automatically, especially when a code hosting service does not have, like GitHub, a field for license in project properties.
You probably would also want to mention copyright terms briefly in
I also have to note with regret, that many amateur free software developers neglects these legal technicalities, please do not take them as an example.