These days, Adobe Animate, or as it used to be called, Adobe Flash, is the most popular animation tool in the world. However, it's oldest versions (a. k. a. FutureSplash Animator under FutureWave Software and Macromedia Flash 1, 2, 3 and 4 under Macromedia) were order only, as in, you had to order a physical copy of the software directly from the company. It wasn't until Macromedia Flash 5 that they started using a serial key. What that means is, is that unless you got the old copies of said software, you wouldn't be able to get a hold of the full software since nobody has ripped the .exe file online. What you can find is trial versions of the product. I personally think this software deserves to be accessible today, since it's important to the history of animation. If anybody can find info about this, maybe the full copies of the software, post it to this board.
Also, I contacted this guy called "belaboy" on Tumblr, since a .gif he made is one of the first results you get when you search FutureSplash Animator. He does have the full physical copy, though I am waiting for a response from him to see if he'll upload it.