I've been working on a personal closed source project for some time and would like to make it open source. I've never created my own open source project before so it will be a good learning experience. I have been using GitHub as source control, so once I've written some decent docs on how to use and develop for it etc, it should be as simple as switching the repo to be public right?

I guess my main question is around licencing. I was thinking of going with Apache 2.0 licence just because it seems to be widely used. It requires the licence header to be attached to all the source files, but if I do that now then all the other commits in the past will have it missing. Does that mean some one could pull an earlier version and it wouldn't have a licence? Is it best to start a new repo with the initial commit containing all the code with licence headers? Or maybe is there some advanced Git functionality that allows me to apply the licence header to all existing commits some how?

Cheers.