When is it "official" that a license has changed?

["Jordi Gutierrez Hermoso" <jordigh@gmail.com>]

Hi.

After sending emails around and waiting patiently, I have convinced
the authors of two problematic packages in Singular (bug #383515) to
adopt the GPL. I have emails of those confirmations.

Is this enough, or should I wait until they modify the upstream
sources and change the license information at the top of each source
file?

Thanks,
- Jordi G. H.