You are totally right that the 10% going to a wallet is a concern and everyone should be aware that at any point the dev could run off with the funds. However so far the dev hasn't given us any reason to believe this will be the case and hopefully sometime in the future the plans for setting up a formal auditable charity will be hammered out. Beyond that everyone should expect the 10% to be sold on a regular and ongoing basis to fund that charity.
It'd be kind of a hard scam to pull off in any meaningful way. For that 10% to have any value, BBP would have to have value. Since the platform is based on charity, BBP won't have much value until a transparent charity mechanism is established (you're probably talking 1 sat or less if it got listed on an exchange right now). So basically, the dev(s?) would have to carry through on most of their promises just so they could establish value for the coin, including verifiably using the donation funds for charity, just so at some point in the future they could run off with the balance generated between then and the previous month's charitable donation. I mean, hypothetically it could be worth it if the value rose high enough, but it seems like it'd be a lot easier and less risky to do a scam ICO and just make off with the BTC/ETH.
Even in the worst case scenario and the devs ran off with 10% of 1 month's currency generation after building up value, that wouldn't be catastrophic. All the code for BBP is on GitHub, the community could easily fork the project, change the donation address, and figure out a community-driven way to manage it.