OpenDax is good but this doesn't support all altcoins

If you don't want that suggestion above then there are many open-source crypto exchanges I gathered some of them a year ago and here's my list below.

Check this one below the design looks the same as Binance but in the Chinese version, you can maybe edit the language to English.

- https://github.com/jammy928/CoinExchange_CryptoExchange_Java

Other open-source crypto exchanges below.

- https://github.com/wlox/wlox
- https://github.com/3s3s/opentrade

These one don't know if safe or not but you can check the source if is safe or not

- https://github.com/GMX9/Crypto-Exchange-PHP
- https://github.com/huokedu/Open-Source-Cryptocurrency-Exchange