Is it ok to make giveaways with humble bundle direct links ?

Did you set it as a gift rather than a key when creating the giveaway, and sent it by mail after it ended ? I tried to create a giveaway with one of these but I got this message : Only Steam redeemable keys, or gift links from Steam or Humble Bundle are allowed.

games from old humble bundles don't show you the key, you just click a button and it direcly redeem to your Steam account

you can put the gift links in there just like you would with a key.

Yes, that's the one. The new SG takes those gift links, just like it will keys. As long as the link is a good one (game hasn't been redeemed), then you're good to go~!

No, I don't mean that. I know you can use this page for giveaways, I was talking about the page that you get in your mail box when you use this page

No necessarily, I think you can claim this page to your Humble account after you redeem the game so no one else can see it

Perhaps you must make the game link into a gift link, then copy that gift link for the giveaway.
That, or sending the link through Steam (by adding the winner and pasting it into the chat), or alternatively by email. It isn't really important how the winner gets their game, as long as they get it.

I usually select "Gift" when creating a giveaway, then I just add the winner and send the link through the chat. :)

games from old bundles don't show you the key, they activate directly from the page