Resolving dependency on a senior colleague before deadline
Circumvent that person as a stop-gap. Specifically:


Fix a time shortly before the deadline when you are certain you'll be able to make the submission setting the information yourself.
Guesstimate to the best of your ability what the correct value for the licensing field should be - erring on the side of making data openly available (i.e. something like CC-BY-SA or public domain).
Regardless of how you communicate with the person who's supposed to take care of it - when the time comes, if s/he hasn't done it, you do it.


If that person gets upset after you've applied this stop-gap - you'll be able to argue that it was necessary so as not to miss the deadline, and that you're sorry but you had no choice. You can also say that if s/he believes somethinh else should have been put in, you both can always communicate the change to the organizers and say the original input was an error.

As for an effective way to "prod" this person, I can't suggest something particularly great without additional information, but:


You could talk to someone who's in close contact with him/her, and on speaking terms with you, and get them to try to apply their influence.
You could bring this up in a public forum where s/he is also participating, e.g. a group status meeting.
You could let him/her know about your stop gap in advance. That's a bit risky because they might object and you may end up having to directly disregard the objection.