It sounds as though you fell into goose keeping without any preparation and that is often the worse way to start anything as you end up making mistakes that have concequences for later.
Before I say anymore, let me ask you a couple of questions. If you were buying a dog, would you go to a reputable dealer who has bred that dog, who can tell you about its breed characteristics and its socialisation and where you at least meet the mother of the dog. Or would you go and buy a dog from a dealer who's doing a flea market. This person is selling lovely looking puppies, very cute you fall in love with them, but you know nothing about the conditions they were kept in or the way they have been handled/socialised?
You would avoid the flea market seller as the dog probably came from a puppy farm where its been given no social skills and probably badly bred and its going to lead to huge problems later.
That is the situation you have got now with geese These geese have spent a minimum of four years being wild and not handled or socialised. By the sounds of things they had minimal handling/socialisation before that and quite possibly were badly treated and view humans as a threat.
I can catch and handle my Embden geese, they also know by the sound of my voice when they are in trouble for raiding and know to scarper quick sharp!! :roll:
Also my birds are fastened in a hut every night and know the routine so well they stand waiting at the door as thats where I feed them their grain.
I would suggest that since these geese are accustomed to you calling and giving grain, that this can be used as a starting point towards taming/penning.
Put a hut at the side of the lake where they are or where ever they are normally fed and every evening or when ever they are normally fed start calling them and throw just a little grain on the floor near the hut for them to see and eat, then put the rest of the feed just inside the hut.
So to eat it the geese need to just step inside the hut. Continue doing this same time same place every day except that the feed every few days is moved a little further back inside the hut.
Geese are naturally suspicious of anything new and change in routine, so its going to need a lot of perseverance by your friend. Once the geese have accepted this as the norm try offering grain either in by hand or on a scopp thats being held out to them. Once in a routine they accept it as the norm and will continue in it.
That said it is going to be a very slow and gradual process over months and in the mean time there is a sick goose needing treatment. Given that it can't be handled or got close to, then it is going to need advice from the vet about how to catch and handle it.
I would very strongly suggest that your friend arms himself with some knowledge about how to care for the animals in his charge and obtain a book on goose keeping.
There are plenty around, there is one I can reccomend http://www.amazon.com/Starting-Geese-Katie-Thear/dp/0906137322/ref=sr_1_1?ie=UTF8&qid=1312798449&sr=8-1 but this is written with the UK in mind and sometimes things don't translate well, so best your friend does some research into the most suitable for him.
Next time you get the urge to buy geese go to a breeder who specialises in the breed, it will be so much better.