It's been a long time since anything has been Foxed. AvP - Redemption actually reached out to Fox to make sure they were okay. As mentioned above, Predator: Dark Ages got through their Kickstarter without any bother (and from what I understand, they hadn't contacted the Dark Ages guys at all).
It's becoming more and more common practice for fan films to actually have involvement from some people in the film industry or people who worked on the original films (it's quite abundant in Star Trek fan films now) and to be crowd-funded. It's really increasing the quality of these projects.
And at the end of the day, it's a non-profit project, just for the love of the franchise.