There is nothing stopping a GPL project using MIT-licensed code except for lack of desire to do the work. They are one-way compatible.

It really depends. If the contract gives ownership of the work created to the purchaser, he has no rights to it whatsoever. Moreover, trying to do a clean room implementation of your own code is almost impossible without help. A permissive license would give the purchaser unlimited use of the product, including resale while still allowing the producer unlimited use, as well. If the contract is written correctly, the producer might even retain ownership, with the right to use different licenses, while the purchaser would have few or no restrictions.

I’ll throw my opinions in here.

If you’re publishing a standard or a reference application, a permissive license makes sense. What better way to guarantee compatibility than being able to use the reference code in your product. This is what happened with the TCP/IP stack, and it was used in its original form in Windows for years.

If you’re making something that you want to build a community around, something more akin to the GPL may be more aligned with your goals. The nice part is, you can include MIT licensed projects as part of your GPL project. This means there is nothing stopping you from building your standard with a MIT license while building your community-driven application using GPL, maximizing the reach of your standard while reducing the risk to your community.

Note that either option opens you to EEE (Embrace, Extend, Extinguish), the GPL option just takes an extra step (clean room implementation of a published standard).

Or my mom.

Me: Don’t just click OK without reading the message first.

Mom: Don’t click OK. Got it.

This is part of what helped the I love you virus to spread. Not too many idiots would open a file titled ILoveYou.txt.vbs, but even some smarter people will turn their brains off if they get a file titled ILoveYou.txt, possibly even me, except the first thing I do with a new computer is unhide file extensions.

I was going to say they didn’t used to require that, but that’s about 20 years ago, now…

Those checks go to the larger YouTube channels, not people like you and me. Did you mean something different?

/s