How is «歐付寶 allPay» related to «綠界 ECPay» and «智付通-Spgateway»?

Extensions 歐付寶 O'Pay (allPay)
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It looks like «歐付寶 allPay», «綠界 ECPay», and «智付通 Spgateway» have almost the same API.
How are these payment services related to each other?