Doesn't every Joe Blow and his dog have their own manifesto nowadays?
Yes I'd agree it's losing its original sincerity, so adding one would be to water down the conviction of manifesto's that mattered. So I'm demoting this slightly, it's not as much a manifesto now as it is a pledge.

When computing joined the ranks of technology its purpose was clear; it was an aid to humanity.
Great men with that message firmly in mind paved the way for computing to achieve good things. Men like Linus TORVALDS, Jimmy WALES and yes, Bill GATES who saw the big picture and has done so much good in the world since. Not only with money, but his time.

More recently, computing has become a dog-eat-dog world of backstabbing, profiteering and patenting. Enter the cruel and malicious exploiters, steve jobs, mark zuckerberg, tim cook. Where there is promise, there is profit and where there is profit, there is a force that appeals to the worst in man. And it pulls most fiercely at the worst of men.

Perhaps it will never be what it was before.
But it is worth not losing the big picture, so that's my pledge.
I'll keep this big-picture firmly in mind, like the men I admire most, did;

Technology is for the good of humanity.
Be careful not to confuse theirs with yours.

my pledge,
mark that I should ever contradict it.

P.S. If you like Jimmy WALES as much as I do, consider donating to WikiPedia every year, you get a thanks from Jimmy that almost feels like you know him =). Well worth it!