Hello, I'm a (broke) college student interested in animation, and I've read on the internet that there's a specific version of Adobe Flash that is claimed to be "legal" to use for free (version MX2004). I don't wanna be an outlaw, and I'd rather avoid using it if it affects Adobe in any way (though I doubt it'd do much since it's a piece of software that's 16 years old). But I wanna know if it's possible to use it for professional endeavors.
No version of Macromedia Flash, Adobe Flash or Adobe Animate has ever been free.
If I understand the story correctly, there was a time when Adobe put CS2 product up for you to download whatever you wanted. That may be what you have read about. The catch is that it was done because the CS and CS2 installers no longer worked. Once you had done the download you would still need to have a license for the software.
It is possible that CS owners effectively got a CS2 upgrade without paying more money, but they had bought CS previously.