In essence open source projects are vendors as far as ntp.org is concerned and you can use their service but have to obtain a vendor zone for that. The formulat

In essence open source projects are vendors as far as ntp.org is concerned and you can use their service but have to obtain a vendor zone for that. The formulations are indeed not as clear as they could be but after reading the ntp.org page a couple of times there isn't really any other meaningful way to parse it.