I retract my previous statement! If you're already doing the Co-authored-by, that is fantastic, then their names are clickable on GitHub, and the developers themselves will be able to directly interact through their own GitHub accounts if they are @'ed by the customer. This is great. Definitely advertise that aspect.
In general my advice is this is one of those gray area markets where it is extremely easy to exploit workers, so you should do everything humanly possible to make sure that:
a) workers in this program are progressing with the goal being they can eventually "graduate" to the point where a middle-man is not required. This won't be possible across the board but an evil version of this startup would be designed to keep workers in this situation as long as possible, so just don't be that.
b) Allow customers who want to direct hire specific workers to do so seamlessly and don't do hefty referral fees that are enough to stop a lean startup from being able to pull the trigger. I've personally witnessed startups unable to pull the trigger in such situations because they can't afford to "buy the person out" of whatever referral company owns them. Don't be like that. If you absolutely must do a referral fee, structure it so they at least get back the money in credits with your program or something.
c) Treat workers like the assets they are -- each worker that eventually gets a job through your program becomes a marketing asset that will drive referrals from their home country when they eventually find success and tell their friends how they succeeded. Make sure you have created a positive enough experience for them that they will actually recommend you and dear god give them referral fees when they send you someone.
That's my free advice
