GitLab offers free security checks for opensource projects (
https://about.gitlab.com/blog/2018/06/05/gitlab-ultimate-and...). Enabling these checks is as simple as this one-liner (
https://docs.gitlab.com/ee/user/application_security/sast/in...):
include:
template: SAST.gitlab-ci.yml
Now do the same with Dependency Scanning, Container Scanning, DAST and License Compliance if needed.
Note that Auto-DevOps enables this automatically.
On a general note, I agree with you, Security should be available out of the box for everyone. I created last month this issue for this purpose, feel free to comment or watch it.