Pesto is a 12-week training program where we teach software engineers in India how to be effective remote employees and then help them break into international tech careers via full-time remote jobs.
During the last four weeks of training students complete an open source apprenticeship, where they contribute to popular open source projects for free.
The goal of the apprenticeship is to give engineers hands-on experience working in a fully remote environment. Contributing to open source not only helps them sharpen their technical skills but also refine their soft skills like learning how to communicate through Github issues, collaborating across time zones, incorporating feedback from code reviews, etc.
Any maintainer can submit their project. However, students choose projects based on their areas of interest and the project's likelihood to help them get a job. 
We do not expect any technical mentorship beyond what would be given to other contributors that make pull requests to your project. The students have access to our senior engineering teaching staff to guide them if they get stuck.