I would like to suggest that we move to not using FQN in the phpDoc and instead import the relevant classes. Most will already be imported and this will make it less likely that one is not updated if it's namespace changes.
For consistency I would also suggest that we use shorthands for scalar types int/bool vs integer/boolean.
Lastly although it might not be consistent I think it would be a good idea to use ClassName for hinting array types over array<ClassName>, when the key type is unknown, since it's supported by more tools.
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.