One difference is that TravisCI offers free Mac servers for OSS, but you can only get Mac builds if you pay for CircleCI. But that isn't really a problem for Pdepend
But for DevilutionX we have to use a combination of CircleCI, TravisCI and AppVeyor and that still doesn't cover us for Haiku and BSD :/
Back on topic :) I have solved all PHPStan level 3 & 4 issues on my local system. But will wait with a PR until the current ones are merged as it will be easier to clean up and avoid conflicts that way.