That's what we did, too. As a company, we formalized our open source R&D activities (https://github.com/RaRe-Technologies https://github.com/RaRe-Technologies)

That's what we did, too. As a company, we formalized our open source R&D activities (https://github.com/RaRe-Technologies https://github.com/RaRe-Technologies) and launched a "Student Incubator" programme. Junior people around the world get to benefit from the mentorship, and we get access to talented people early on. Without that much internal risk, since it's open source. The problem is exactly as you describe: scaling. Mentoring is an extremely time-intensive process and when things go rough, such "charity" activities are the first to suffer.