Source code openness and Ubuntu bounty projects

[Jung-woo Sohn]

Hello,

Can I ask a quick question about how Ubuntu bounty projects go on? I am 
a grad student working on the effect of profit incentives on open source 
projects with bounty.

My question is as follows. When you engage in any bounty projects, does 
the source code need to be kept open all the time or can it be closed 
until the project completion? I know that all projects will be 
eventually open to public but I am wondering what happens to the source 
code openness while the bounty project is ongoing.

Thank you.

Best regards,

Jung-woo