I think something intermediate between his two solutions could work very nicely. Perhaps a set of competing translation repositories, and asking the user which if any to use. There's still a trust issue with the translations, but that's right the problem we already have with open source, and the downsides are probably more limited security-wise. You could still have the option for the user to supply a translation. Having common schemas that apps commonly target for bidirectional translation increases the odds that you can have serendipitous inter-app translation using only "first-party" translations by going through the common format.