Relative licensing restrictions of Ethereum and other projects- Open Source? Is Ethereum open source? 

I've heard different things from different people. 

Stephan Tual has written: 

"Everything at Ethereum, including our website, our tools, our whitepapers and of course our all of our software and compilers are 100%, wall to wall open source and under the GPL."

But then what about the Ethereum Foundation? 

How does the open-sourceiodicity of Ethereum compare to that of Bitcoin? How does it compare to that of the proposed "private blockchain" Hyperledger project?
Is Ethereum open source?


Yes. You can find all the source code on Github.

Technically, Ethereum - as in the idea - is open source since you can read the full specification in the yellow paper. 

Ethereum - as in the software - is open source and you can find all major and minor implementations on Github: geth, mist, etc. (GPL, LGPL)


  But then what about the Ethereum Foundation?


Yes. You can find a general statement here