Reactivating the topic as I managed to get a first version of Beckhoff ADS integration working with openHAB. It works from Linux thanks to Apache PLC4X. This is java-native integration. It requires no DLLs and no license (let say) to connect if you know your PLC symbol table.
Please follow below topic if you find it interesting:
Currently I lack Beckhoff device for testing thus anyone who is capable of handling this integration is welcome.