The ISRG seems to have two projects of this type mentioned on its website: an improvement to curl (https://www.abetterinternet.org/post/memory-safe-curl/), in which the ISRG funded the curl author directly; and an improvement to httpd (https://www.abetterinternet.org/post/memory-safe-tls-apache/), in which Google (via the ISRG) are funding an httpd committer.