There were quite some KNX hacks in the last 2 years as searchengines like shodan easily show you forwarded KNX networks. And I think there are no ways to remove the passwords on many devices, they need to be sent in to the manufacturer to be reset or you need to hack the eprom/flash yourself anyhow.
Gira Homeserver is fine to visualize your installation and have your logics running, but to integrate with other smarthome standard it’s quite inferior to most other (even open source) solutions. I use ioBroker myself, I know of alot of guys running openHAB or FHEM for that. Not sure about Home-Assistant though, I tried it a few minutes and did find several devices missing that I am running here. So it’s not an alternative to ioBroker for me. But at least is has a very moden GUI, which is where ioBroker sucks! But nothing can trump Gira Homeserver (experte) ugly GUI wise ;)