The terminal profile describes which particular features regarding proactive sim or sim application toolkit a given phone supports.
This is not only important for SIM application / SIM toolkit developers, but it is also an important factor when trying to analyze the potential threat that can originate from a malicious SIM card attack.
I personally see no reason why my phone should ever report its GPS position to the SIM card, or why the SIM card should be able to re-write the nubers I'm dialling. Yes, there are cases where such features are useful, but then they should be explicitly enabled by the user, and the default should be that they are all switched off.
Who knows, after all, with some attention to this problem we might still see a SIM firewall / proxy, that you can put between the SIM and the phone to prevent any of those features from being (mis)used.
So all you need to do to contribute to the database is some way how you can read out the terminal profile from your mobile phone(s), and use Kevin's tool to upload it to the public website. And hwo do you read out the terminal profile? For example by using Osmocom SIMtrace to sniff the communication between SIM card and phone.