An OEM license is intended for system builders and manufacturers (like Dell, HP, or local PC shops). When you buy this license, you are technically acting as the "system builder."
: Sites like Newegg or Amazon (when sold directly by the platform) offer legitimate OEM "System Builder" packs. These usually come as a physical DVD or a scratch-off key card. buy windows oem license
You can find OEM keys through various channels, ranging from official distributors to "grey market" resellers. An OEM license is intended for system builders