I see that 1.5 version is available at thewitcher.com, but it's showing as unsafe to download. Both GOG and Steam only have 1.4.5 versions available. Curious what the deal is.

I don't know about galaxy, but the stand alone version here on GOG is 1.5

The ingame version will show as 1.4.5 but if you hover your mouse over the the witcher exe in wherever you have the game installed will show as 1.5 . It`s a little confusing I know but yes it is the latest version. Also of note if you try and install a 1.5 patch you will get a message stating that it cannot identify the installed version.