How do you copyright/license software based on MIT-licensed open source code?

Question

I am a former developer that codes in my spare time for fun and to maintain some level knowledge in the subject. So I found an interesting proof of concept online. I saw the potential to modify it and to make it something useful for a certain industry. So I modified, tweaked, and added to the code, making it a Firefox extension.

The proof of concept is covered by an MIT Open Source license.

So the code is 60-70% original. I added the rest and made it useful. I demo’d the extension to a small conference and I was immediately offered money to sell or license it. Pretty cool for a weekend project. It was something I wasn’t expecting.

So, first question. What’s the first step? Can I copyright my program if it is built off of an open source project? How and what kind of protections does it give? I don’t know the first thing about licensing.

Next, how do I control the distribution? A general amount was thrown around for the use of the extension (over 100k). So I don’t want it in Firefox’s App Store or whatever you call it. I also don’t want to just email the extension and then they email it on to the next guy or sell it themselves. Any advice? Anyone been in this situation before?

Answer 1

1. Since the original code is MIT licensed, you can use it any way you like, including turning it into proprietary software. You can use any license you want. You only have to give the original authors credit as it is required in the MIT license.

2. The question about controlling distribution is hard to answer since it depends on the type of software and how it is installed and used.