Good question! Games will be selected based on their current condition, which means everything should be ready to go to print when submitted. The idea is that Long Tail has no expectation or requirement for chosen contributors to do any additional work whatsoever. 

However, once the games are selected, there are two windows in which the files can be updated: January (before the prototype is printed) and March (before the final product is printed). This is entirely up to the contributor if they would like to make final modifications. 

So basically people are very welcome to make 'alpha' submissions to the jam, with the intention to update the game before production. However, the selection process cannot take these planned updates into account, and will be made based entirely on the games as they currently stand. I hope that helps!