You can literally steal the code of the grant app. Everything that is granted must be open source. What do you mean with undercutting the price?
Everything covered by the grant being open-source doesn't mean that every service or feature is entirely free to use or that there can't be additional related projects, occasions, benefits, services etc. that are for premium customers. There are a lot of freemium models or etc. Grants mean that the financial incentive is to just offer everything for free, which means we have to be grant-financed forever. Which is what a lot of people want, of course. Free shit forever.