Perhaps you weren't paying attention when you read what Carmack wrote. Or perhaps you didn't even read it, because you're suggesting something that has absolutely nothing to do with the tweet.
Carmack said he wishes the source had been released under the BSD license instead of the GPL.
You're saying that it's not easy to conclude that new versions of Doom would exist if the sources had never been released at all.
If you're trying to troll and suggest that it's not easy to conclude variants and updates would exist if the sources had been releases under the BSD license instead of the GPL, then we all know that's completely ridiculous, so I'm giving you the benefit of the doubt and suggesting you either didn't read or understand the tweet.
If you want to suggest there'd be less variants and versions? That'd be reasonable, but you're not saying that.
Carmack said he wishes the source had been released under the BSD license instead of the GPL.
You're saying that it's not easy to conclude that new versions of Doom would exist if the sources had never been released at all.
If you're trying to troll and suggest that it's not easy to conclude variants and updates would exist if the sources had been releases under the BSD license instead of the GPL, then we all know that's completely ridiculous, so I'm giving you the benefit of the doubt and suggesting you either didn't read or understand the tweet.
If you want to suggest there'd be less variants and versions? That'd be reasonable, but you're not saying that.