It would probably take two years of coding in C to do real work for those projects. If you want to make an impact, fill in the gaps in their man-power to do the things that are not writing software features.
Go to their bug trackers and start working on the smallest bugs. Or write extensions for the most popular new languages to use their libraries or apps, so new programmers can take advantage of the existing crypto. Or write or update documentation. Or write user-friendly guides on what people need to use and how. Or fill the holes in their test routines to find new bugs faster, and build new test platforms for wider platform coverage. Or track down performance bugs.
Go to their bug trackers and start working on the smallest bugs. Or write extensions for the most popular new languages to use their libraries or apps, so new programmers can take advantage of the existing crypto. Or write or update documentation. Or write user-friendly guides on what people need to use and how. Or fill the holes in their test routines to find new bugs faster, and build new test platforms for wider platform coverage. Or track down performance bugs.