This is NOT an April Fool's joke. Sorry, yes it is an April Fool's joke
I've just downloaded GPO5 again (a clue from elsewhere) and I've discovered that the installer is now version 5.01.
It installs the latest update to ARIA, namely player 1.872 with the same engine.
There's no visible sign on the download page that it's a new version (that I can see).
Maybe I'm going blind as well as deaf. (Daft is a foregone conclusion.)
It also reloads all the samples again, which is a pain in terms of time taken, and I'm not sure yet whether it's necessary.
Quite what has changed, apart from the ARIA player version, I'm not sure at this time.
If I discover what, I'll let you know.
If you discover please post your findings.