Here's the full video of Neo himself awkwardly-but-kindly offering up his seat.
Not much is really known about this, but that's sorta the point - Keanu hanging out with a homeless guy is no big deal for him. He REALLY treats everyone as equals, since most REGULAR people usually don't give the homeless the time of day, let alone Hollywood movie stars.
What is known is that in September 1997, Keanu hung out with a homeless guy in West Hollywood and just chilled with him for a while.
While there's a popular urban legend that Reeves directly donated about $80 million to the special effects staff of the Matrix sequels, the truth is a little less awesome and a little more complicated than that. What Reeves did was give up a substantial piece of his contract (involving backend profits, which would have ended up being around $38 million) to relieve producers' fears that the special effects budget was far too high and would render the film unprofitable. The reality of this is that his decision to give up that aspect of his contract likely saved scores of jobs from being cut for budgetary reasons, so he's still a pretty cool dude.
He also gave each member of the stunt team a Harley Davidson motorcycle, valued at over 6,000 Euros. Whoa.