Through the normal way to do things you could not get access unless you use his email.
Now say if you have the license owner say set the email for the license to say a catchall account like email@example.com
you could use that email but the long and short of the process is only one of you can be verified on the forum since the verification system match's forum users against email's on file for license holders to verify them. Since you can only use a unique email on the forum then only the license holder themselves can be verified.
He could download the mod you want to use for you.