[Erwin]

A Humble Bundle is a last-ditch effort to sell an old game -- appealing to hoarders for the company to gain some publicity (as some just give all to chaity). The last "2K" bundle had $360 worth of games -- for $8.97 and only a small proportion of that comes back to the company.

If you want to support Linux as a platform, I recommend you donate at higher e.g. $50 or $100 tiers to Kickstarter projects that have Linux stretch goals and be vocal about your donation.

Paying 5% of the sale price years after the game has come out doesn't strike me like fruitful.