Satoshi Nakamoto released Bitcoin SHA-256 under the MIT/X11 Open Source license for the specific purpose of allowing the creation of other versions of Bitcoin (aka Alt-coins).
The opposite is true, in fact. He released it under the MIT license so that people wouldn't feel the need to rewrite the main Bitcoin client:
If the only library is closed source, then there's a project to make an open source one.
If the only library is GPL, then there's a project to make a non-GPL one.
If the best library is MIT, Boost, new-BSD or public domain, then we can stop re-writing it.
I don't question that GPL is a good license for operating systems, especially since non-GPL code is allowed to interface with the OS. For smaller projects, I think the fear of a closed-source takeover is overdone.
First, thanks for the informed response as I cannot get into Satoshi's mind to learn his intent for using the MIT/X11 license.
That said, I read the thread and am confused when I reread your response (or think you may be confused).
Are you claiming that Satoshi chose the MIT/X11 License (over GPL) so people would not create alt-coins by rewriting the main Bitcoin client? That's what your response in the context of my quote seems to imply. I could find nothing of the sort in the Satoshi thread you quoted as he seemed to be discussing the creation of another Bitcoin client that would utilize the same Bitcoin blockchain and makes no mention of alternate blockchains.
Aside from Satoshi's intent re MIT/X11 license, do you believe that there does in fact exist only one (1) official Bitcoin?