isthereanydeal.com lists only legitimate retailers, no second hand/grey market sites. Not exclusively Steam though, so check on the site before purchasing (though usually every website will be selling Steam keys except like Epic Games Store, Microsoft Store, Ubisoft, EA Origin).
You can also link your Steam wishlist, set up alerts for when a game falls below a certain price, etc.
Ok, I might be misunderstanding here, but since committing changes is allowed for everyone, doesn't this mean fixing bugs is something you could do? You'd just be stuck with all the other rights as well until someone else makes a change.