Just tell everyone you're dealing with that your primary purpose is getting rich with the software.

Don't tell them you have always been and always will be open source, just until you're big and give the middle finger to OSS in order to get richer.

A given piece of open source code when licensed is always open source. Changing the license doesn’t retroactively do so for the previous code.

There is no lie.

You apparently are not familiar with the concept of software maintenance, upgrade, security patches. Or completely ignored it when wrote this comment.

No. No no no. Don't weasel-word out of this with bullshit technicalities.

The phrase isn't "FooBar v3.11 is free and always will be".

There is no version number in the phrase, so the common understanding is that the product and every version of that product will always be free.

lol. If it helps you cope, imagine the company died, another company forked it with a new license.

Same thing, same result. We are literally discussing this in a thread where a prominent maintainer died. Nothing is forever.

There is no way to guarantee something will be the same forever.

Again, fork and move on if things change to your dissatisfaction.