The situation is that the source is unavailable, so it must be reverse-engineered=/=reconstructed. That's a BIG task. Thus there's likely no way to out a good estimate on it.
On or about 5 Aug Oswald posted the new XAMPP 1.7.4 Beta 1. It can be found here: http://www.apachefriends.org/en/xampp-beta.html The xampp controls have been released under the GPL. They had been previously released under a modified BSD license. I think Oswald doesn't intend to make the source available until it's out of Beta though, so we'll have to wait a little longer.