As a researcher with many articles in the ACM library, I have to say this is a masterclass in hypocrisy. Obviously, lawyers can decipher the terms of ACM publishing contracts and Creative Commons licences to determine if this will be acceptable or not. But ACM is not a company, it's a non-profit founded in 1947 to represent scientists.
I would be surprised if a majority of ACM members were to say yes should we ask them (but ACM is not known for such democracy). Along with book authors, we are one of the many people that provide the knowledge and expertise on which large tech firms train their models, and get nothing in return. Actually, life is getting worse for us: extra workload in universities with students' AI use, a completely broken peer review system, etc. Hence the irony of ACM thinking about licensing, and only licensing, at a time where this is the least of our priorities.
You mean the knowledge you gathered with public grants, with a public paid salary, yet don’t want to make freely available to the public?
Yeah, too bad
As long as we are going toward a world of abundance where money doesn't mean much and the main currency is time, I can't complain. I will subsidize that with my brain power turned into ink on paper.
If you don't hold a patent for the use of the knowledge you published publicly, you can't prevent others from using the knowledge. You enjoy the prestige attached to the idea that you're an academic who participates in giving away their knowledge but then you play this game when that knowledge would actually be useful as opposed to being read by 3 other people in your special area who sit on your various committees in your career, now you want to forbid the use for culture war intra-elite signaling reasons.
You don't own the knowledge you put out there unless you have a limited time valid patent. The rest is absurdity. If you want to keep your findings to yourself, keep them secret.
If it was a non profit that trained the model - would that change your mind?