While the gesture is noble, you may end up hurting him/her in the long run. If media start linking to your domain rather than to the appstore page, he'll have broken links and lost pagerank if/when you decide to do something else with the domain.
Unfortunately it's even easier than that to destroy a domain's "Google reputation." Go on fiverr and buy a ton of spammy links, direct them at your competitor. It runs about $5 per 100,000 links last time I checked. (I've never done it, but it's a common blackhat technique).
What a noble gesture. On an unrelated note, I have some domains parked of my own, and I realized this is a great way to use them - help drive traffic to apps. And perhaps if he makes enough money from the app, he'll buy the domain to make a landing page for it. Plus it's really great to see a domain thats not parked with those stupid ads.
Having said that, what a great domain!