The files to run Decimator come with Daz 4.5, but the serial code to unlock it is sold separately. Same goes for aniMate 2, which gives you a trial version before defaulting to aniMate lite.
As I understand it (but please correct me if wrong), if you have a serial for DAZ Studio 4.0 Pro that you got by buying the product, i.e. before the price was discounted to zero, then you will automaticaly have Decimator and Animate enabled. I have read that this serial will also work with 4.5, both the stable version and beta.
I’m about to replace my 4.0 Pro with 4.5 Pro and will report back as I have a pre-free serial.