GoG is trustworthy.
I'm sure they would never sell my contact info or anything either..

The game is from 1994... Safe to say no more updates are coming.
If they made changes to make it work those changes might be updated.
While your caution is commendable it is bit excessive; online game vendors and publishers are perfectly safe.
It's about convenience in finding an untainted patch downloaded through steam(yes a vendor that is perfectly safe), there's nothing excessive about it. You push a button to check for updates, no searching needed, no worries.
Steam takes 30% of every sale... Why should another online vendor like GoG agree to that?
yeah but a 100% of nothing is still nothing right?

Depends on what GoG intent is. Are they doing this to increase their user base or are they doing this to increase sales?
Having access to Steam's large user base might be worth giving up a certain percentage for increased sales. But if GoG is only looking to increase their user base then selling it exclusively from their site would make sense.