You make it sound easy =).. To make things easy for you ill give you an analogy.
For example
You make a unique game lets say your original MMORPG,, so the game you made became popular..
So other other game devs now wondering how you did that.
As your game progressed from ver1 to ver10
You see other devs want to recreate.. Your game in their own way.. But sadly they always somehow failed its either while recreating they made mistakes which we can call as BUGS.
So since you are good you made ur ver8 client files to be public..
And thats it.. Since you make it public other devs now makes your ver8 client files to be their basis... Base client
So now your own game also has progressed from ver10-ver18.
So other devs now wants to get ur latest client files but sadly.. As you a game dev its not easy just to give it away.. But you did give them your ver 8 Client and you think thats enough.
As other devs frowned. Since they can't get the latest client they improvised..
From small things to big things....
But there is only one problem. As they want to recreate things from later version they encountered a major problem they can't just recreate things from later version bec they realize that their base client is only 8 no matter how hard they try, having a base client of ver8 has its limitation.
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Lets say we recreate somefiles from later version we can't know if its working bec. We cant test it using Ep 8 files =)
I hope you did understand the analogy =)