Once you open source, can you take it back?
mdasen: Yes and no.Let's say I put something under the GPL and you download the source.  Later, I regret that and don't allow more people to download the source.  You (as someone who has downloaded it) can still forever use, transmit, etc. it under the GPL.  So, people that want a copy of the source can get it from you even if they can't get it from me - and there is absolutely nothing that mandates I continue to give out the source if it's mine.  I then add to it and make a cool Project 2.0 that's closed only and based off that old GPL code.  That's perfectly fine.However, let's say that I took some GPL code, modified it and distributed it.  Now the codebase isn't all my code - it's also partly one or many other people's code.  I can stop distributing it all together, but I can't distribute it and not the source code.  BUT, what if part of my 2.0 closed source version development was eliminating all the GPL code from it!  Then I can make it closed.Basically, if the copyright is your copyright, you have free range.  You can't take away the rights of someone who already has the code under the GPL, but you can stop the GPL thing from going forward (unless the community builds a better fork off your old GPL code).  However, if you're using other people's code in your program, you're stuck with the GPL unless you can get the authors of the other code to exempt you.So, he can't un-open-source the contributions of the other people, but he could replace them.  One of the flaws in the GPL is that you have to wait for one of the author's whose copyright is infringed to sue.  Courts have sometimes held that intended third party beneficiaries have standing, but that's a lot more murky since you're then claiming that the original author created something for your benefit that an intermediary is stopping you from using.