The consent agreements are agreements between the government and AT&T. They arose because neither side wanted to find out if AT&T was breaking antitrust law. So that the consent agreements and cases arose as a result of antitrust regulations is true. But when you say "the legal theories of when and how to apply antitrust regulations" has changed, that is not supported by the consent agreement because those agreements are not enforcements of antitrust regulations. Similarly when you say "the law as written has not changed, but the way it's enforced" has, that is also not correct in this case because the consent agreements/settlements are not enforcements of laws. I suppose you can argue that if the AT&T case happened today that AT&T would be more likely not to settle because they would feel that they are more likely to win because legal theories have changed. That is in any event it is a different matter than your claim about the enforcement of antitrust laws which did not occur in the case of AT&T. Also note that Kodak was decided in 1992 and is still considered good law. In that case the court found that Kodak was in violation of antitrust law. And that case is still essentially the basis for most (all?) antitrust cases that have been brought to court since then. For example the recent Epic vs. Apple case was just about how to define the foremarket and aftermarket for the variously tied products in the iPhone (like Appstores and operating systems). Nobody has argued that Kodak itself is invalid due to a change in legal theory. You may see a difference in that the government sued a large company in the past but hasn't done so recently and I think that is true. But your claim that it is due to a change in legal theory or enforcement of law is not necessarily true. None of the large tech companies today are nearly as dominant in their markets as AT&T was. The company which most closely resembles AT&T in market control is probably Google in ads but even then it's not even close to what AT&T was doing which was complete control over all US telephone lines and on the phones themselves with explicit contractual agreements that you could not try to make your own phone and use their existing network. I imagine that would violate the law that came out of Kodak by a large margin and had AT&T existed in the same way today it would certainly be sued by the US government and lose.

But regardless of your impression, they give loads of stuff away.

I think the point of releasing Go (they were already using it internally before) was just to get free labor to help expand and improve it. They simply had nothing to gain from keeping it private.