My suspicion is that Bitpay is still using bitcore internally but they`re keeping the code private. even if the original team left they could have had new people joining the team and continuing development. Looking at
https://coin.dance/nodes it seems that the bitcore nodes count has been decreasing this year and I suspect this is because users outside of Bitpay move to other solutions and since the node is not maintained anymore there are no new users.
@lautaro.dragan I think I might have a solution although i`m not sure how well it scales. I am using rpc importaddress with bitcoind, this adds the address to the wallet to 'watch' and parses the blockchain for transactions associated with it. this will take a while.. but after that you can query bitcoind with rpc listtransactions and the account name under which you imported the address. As i said I don`t know how well this scales: scanning the blockchain for each address can take minutes depending on the machines (but bitcoind is responsive) and I imagine this adds to the wallet db so this will start using storage if a lot of addresses are imported.
I still have to test some things but it seems like a workable solution for querying txs by address (not sure about utxo yet). The alternative would be a fully fledged explorer like bitcore/insight but this soaks up large amounts of work and people will keep these solutions private most of the time.. it`s a shame bitcore is not maintained anymore