That could happen. It’s the trade-off of that
category. You can seek the wisdom of the crowd and use it to improve
your entry. It would be possible for someone to read your idea and
submit a similar one in the open or closed category. If someone
submitted a similar proposal to yours and did so in the closed
category, you probably never would know that your idea had been copied.
Submitting in the closed category would avoid this situation but would
prevent you from getting ideas from others that might improve your
application. During Knight Foundation’s process of reviewing
applications, we might be able to identify ideas that appear to be
copies and to decline applications that appear to be copies but we
cannot promise to do that. 

Entering
“openly” means you are either confident enough in your own abilities
and track record that you’ll be chosen to do the work even if others
have similar ideas, or that you don’t really care who does the work as
long as it gets done. If someone copies your idea and then submits a
“closed” application, you might not ever know that happened. The only
way to avoid that situation is to submit your entry as a closed entry.

Can
I claim a piece of someone else’s prize if I give them the idea (in the
open entry) that propels their project into a winning category?[top]

Only
if you are a co-applicant. Otherwise, if you comment on an entry you
are doing so freely and voluntarily with the knowledge that you are not
creating any ownership rights for yourself.  It is theoretically
possible for a technology expert with a good entry to meet up through
the comment process with a community expert and want to invite them to
join in as a partner in a revised entry. But that’s up to the original
applicant.