There's no rules in who can contribute to your software (though the part where you have to list the cost of labor in the BoM might apply funnily if you hired contractors
)
Many teams will leave their code up and open during the season. A lot of teams don't share until after the season for various reasons.
On 1675 we work in a private github repository and make it public after the season once we have (usually) cleaned everything up.