Keep your installation files if you still have them.
All of CDP is opensourced... .you just have to compile yourself. So yeah pretty much not going to happen for most people.
I'd make a drive to show value, although I find most open source requires a lot of expertise, (you need to hire a practitioner that know its cold) or you need a support contract. They're are a lot of edges you can run into.
I am in the same boat using the 6.3.2 express edition.
With this paywall subscription thing from Jan 31, will it affect only the Trial and Enterprise edition or will it affect the express edition too ?? please help on this as days are very few to make a plan