If I use .Net Core 2.0 my software must by 'open software' or what?

Sorry for my English.

closed as off-topic by Philip Kendall, Jörg W Mittag, Ben Cottrell, gnat, Neil Oct 3 '18 at 6:44

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions asking for legal advice or aid are off-topic here. You may be able to get help with understanding, applying, and complying with free and open licenses on Open Source. You may be able to get help with legal terms, concepts, language, and procedures on Law." – Philip Kendall, Jörg W Mittag, Ben Cottrell, gnat, Neil
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 2
    No, your own software does not need to be open source. – JacquesB Oct 3 '18 at 6:08
  • This depends on what, precisely, you mean by "use" and "open software". If in doubt, consult a lawyer, not some strangers on the Internet. – Jörg W Mittag Oct 3 '18 at 6:15
  • 5
    @JörgWMittag, the OP is clearly in doubt (hence the question), but advising him to consult a lawyer is bad advice that, if followed, would be almost certain to waste his/her money. – Ergwun Oct 3 '18 at 6:21
  • @Ergwun: I am not intimately familiar with Polish Copyright Law. I am somewhat familiar with International Property Rights Law, but not familiar enough to say definitely whether Polish Law is even applicable here, although I am familiar enough with IPR to confidently say that there is not enough information in the question to even say which country's laws are applicable here. I am pretty sure that only a lawyer specializing in IPR can figure out which country's laws are applicable here, and I do not feel comfortable giving any advice other than "ask a lawyer". So, that's what I am doing. – Jörg W Mittag Oct 4 '18 at 7:39

Disclaimer: I am not a lawyer. This answer is not substitute for legal advice.

You are not required to open source a product developed to run on .NET Core (any version).

To be clear, .NET Core uses a MIT License, which you must include in any distribution of .NET Core. However, this license only applies to .NET Core, and not to a software developed to run on it. Thus, if you are merely targeting .NET Core, you do not have to worry about this. This is the case for most people that use .NET Core.

However, if you take portions of the source code of .NET Core to include in your product, or if you modify and distribute a modified .NET Core, then you should release under MIT License.

Disclaimer: I am not a lawyer. I am an engineer with some legal experience. And that experience is not in sublicensing code that has been released under the MIT license. I say below that your modifications should remain available under MIT License because it clearly states that you shall keep it. Even if my reading on the license is wrong, doing so should keep you on the safe side.

Note: You can sublicense under a different license, however your modifications should remain available under MIT License. If you really want to do this, I advise to clearly label what files or code blocks comes from the .NET Core source code and to reference in source the appropriate licenses in each instance. This is much easier if you can keep all your modifications of the .NET Core source to a separate project.

Modifying or using the source code is the odd case. You do this by going out of your way to take parts or the totality of the source code from the .NET Core repositories and using that in your project. If you are NOT modifying or using portions of the .NET Core source code, you do not have to worry about this. If you want to modify .NET Core for a privative product, in theory, you could negotiate a different license with Microsoft; I cannot help you with that.

  • MIT license is a permissive license, it's not a viral license. You are not required to release your modifications as MIT licensed code. The only thing that MIT license requires is that you keep the authorship/attribution and license text. – Lie Ryan Oct 3 '18 at 23:56
  • @LieRyan You keep the license text, you keep the license. I am aware that you can sublicense. Perhaps I am reading it wrong, I should have added the usual disclaimer, will do so. – Theraot Oct 4 '18 at 1:22
  • 1
    MIT license doesn't require you to release your modifications in any form, even if you use it in closed source software, you can sell an app to your customers and keep the modified code for yourself. You just can't claim that you've written it all yourselves, you have to show the license text in the application (e.g. in About/Acknowledgements section), but your users have no right to demand that you release the code. This is the main point of difference between permissive license like MIT and copyleft license like GPL. – Lie Ryan Oct 4 '18 at 3:32


.NET Core is under MIT licence.

That means you are not required to make your software open-source if you use or redistribute it with your application.

Not the answer you're looking for? Browse other questions tagged or ask your own question.