Yeah, EU now has a short list of 14 countries (and maybe China if they reciprocate) that are allowed in - but each country can choose for itself if it wants to let them in or not, so it's highly recommended to double-check the rules where you want to go (and please don't go unless you have to). I believe Sweden has already decided not to let anyone in until 7 July.
The Netherlands, as usual, is following what the EU decides and letting all of them in - Australia's on the list, too, as well as Canada, New Zealand, Algeria, Georgia, Japan, Montenegro, Morocco, Rwanda, Serbia, South Korea, Thailand, Tunisia and Uruguay.
The metric is 16 infections per 100 000 people or lower, and the list changes every two weeks or as needed.
It's great that they're opening up again to safe areas, I'm certain there are more people in the same situation as me - lots of those countries have passports that are seen as long-stay visas (90 days), and would not have been able to apply for one in order to round off the application for a long-term visa like ours. In fact, the only countries/city-states that now still have that problem are Vatican City, Monaco, and the US.
...I'm hoping that it won't negatively affect the priority of the immigration department to find a solution for those countries that still can't apply for a long-stay visa. Because uh, it's going to be a long time before the US reaches that metric >.> It's currently sitting at a GLORIOUS 787.5 infections per 100 000 people, and growing. *sighs* My SO's state has less than a third of the population of the Netherlands and a few days ago passed the highest number of daily infections NL had back in April.