You are correct that in order for projects to be eligible they must not be seeking profit. This is listed as a requirement on the program page: https://about.gitlab.com/solutions/open-source/join/.
You can see many of the open source projects of significance who are part of the program here: https://about.gitlab.com/solutions/open-source/partners/
> While most partners are also members of the GitLab for Open Source Program, not all are (as some partners are commercial open source entities and therefore ineligible for the program).
Source: https://about.gitlab.com/handbook/marketing/community-relati...
You can see many of the open source projects of significance who are using GitLab here: https://about.gitlab.com/solutions/open-source/partners/