It means we can use any free extension available.
only if the extension author gives written permission to redistribute the extension.
that’s what I meant
But if the extension is free then why did we need permission form author.
Actually this is my first time for any compitition so I don’t know what exactly it means.
Because a piece of software is free of cost does not automatically make it free to redistribute. 
Ok, Got it. I don’t think so any author will refuse to use it.
what if extension developers are participating and they use their own extension, they need their own written permission to redistribute it??
This screenshot is from slack, ask your dought/queries about hackathon there. Organizer are answering all the questions.
Can we use some paid materials like font awesome pro ttf or otf?
I think no.
If some devs will use paid assets then competition can’t be called fair.It should be equal for all.
but why…?
Everyone has not money 
That’s why you can’t use paid extensions in your app.
hmm ok, it was my friend who provided it 
Can I apply now
No
Is it over.
Yes it is over, you should apply before 19 June.
No, the registration closed 11 days ago
It is not over.
You have been late actually