is Ethereum MIt licensed? Can we use it for business purpose?
A note adding to both predecessors:
For "business use" you would need to rely on the piece of software for a long time (mostly). The copyright owner of the various sources (client, core, etc) can switch license to my knowledge and put the further development under different terms. This does not apply to the already e.g. MIT licensed code but could endanger long term usage. You always have to take a look at the foundation structure and influencing powers behind these projects:
- Is there a "foundation" which is non-profit?
- What are the rules of this foundation?
- Can everybody be part of it?
- Are lead figures elected democratically?
- In which legal jurisdiction is the foundation placed?
- How is it financed?
Take a look at e.g. automotive standardization development at ASAM e.V. or the ISO for references of how these organizations should be structured.
It entirely depends on which pieces of the stack you want to use - e.g. which clients, which libraries, etc.
Taking the Geth code as an example, from the documentation:
The go-ethereum library (i.e. all code outside of the cmd directory) is licensed under the GNU Lesser General Public License v3.0, also included in our repository in the COPYING.LESSER file.
The go-ethereum binaries (i.e. all code inside of the cmd directory) is licensed under the GNU General Public License v3.0, also included in our repository in the COPYING file.
Different implementations may well have different licences. For example, the Hyperledger Burrow implementation of the EVM has an Apache2 licence.
To add to @Richard's answer: the Ethereum blockchain / EVM as such is free for all to use for whatever purposes. More information here: https://github.com/ethereum/wiki/wiki/Licensing
The third-party libraries, such as Geth, have various licenses, but I believe mostly they are quite free to use for whatever purposes.