So I’ve got this old Cannondale road frame which I was thinking about building up. It has a Kinesis aluminium fork which appears to have hairline cracks along the fork crown area. The paint is obviously cracked, but is the aluminium stuffed too?
I admit it doesn’t look promising! 
Thanks!
Just looks like the joint of a bonded alum. fork.
It’s probably fine. The crack you see is the one where the leg has wiggled a little bit on the crown. Pretty sure they are glued on but since your weight is forcing the leg onto the crown you should be fine. If you start to notice cracks radiating down the leg I’d probably look at a new fork.
Get a new bike.
sand the paint off to see what condition the metal is actually in
Looks fine to me, try and beat your enemies over the head with it and see if it cracks, or they crack, that will show you if it is ok
I have a good video somewhere of me being beaten with a fork that doesn’t break.
This is fine.
Ride forever, your cannondales frame will die before it’s forks.
I am guessing that movement between the join has cracked the paint so it may be ok. Having said that a new fork is a lot cheaper than dental work and Time off work if it does fail and your would be better to show it to someone in person who knows what to look for than a forum.
crackandfail
don’t sand it back, if there is a crack you’ll smooth it over and it’ll be harder to identify. Just put a bit of paint stripper on it and inspect.
Those kinesis forks are bonded (glued) at the spot you’re worried about. Looks to me more like paint cracking than the bond, I’ve had 2-3 kinesis forks of that era and they’re tuff as. On one set the clear coat did what you see on your fork and it was never an issue. Keep an eye on it but looks fairly benign to me.