They may not imprint, but they can still be tamed. It just takes work.
First, try just sitting near them on the ground with a handful/can/bowl of choice treats. Maybe fresh greens or veggies, mealworms, etc.. Talk quietly to them about anything, you want them to get used to your voice and presense. Toss the treats away from you and near them (gradually you can work the distance closer). Keep your movements slow, nothing sudden to scare them.
Gradually, the treats and their curiosity will bring them nearer. Don't try to grab or pick them up at first, just work on getting them to accept eating close to you.. even from your hand if you can. When you first try petting them, touch them from the sides and below, not grabbing, just stroking. Gradually, you'll cease to be considered a threat to them. You can then work on gradually working your way up in the pets until you can reach the 'feel good' areas. Massaging under the wings or a rub against the earlobes feels great to a bird and not areas they can reach easily themselves to the same effect.
It takes time, they won't tame immediately, but it will happen if you're patient. We had a free-ranged bantam hen come to us that we bought... wild as anything, screamed in fear when we came near, struggled and screeched when grabbed.. after a few weeks of these efforts, I can now pick her up one handed and hold her on her side. She's even fallen asleep on her back in my lap.. this is a hen that never knew a human's touch before we got her.