TravisCI vs BuildBot vs Bamboo vs Jenkins

[Alan Somers]

All of the cool kids are hosting their projects on Github and using
TravisCI for continuous testing.  The integration is fairly slick.
But TravisCI only supports OSX and Linux.  Every time a user opens a
feature request for FreeBSD support
(https://github.com/travis-ci/travis-ci/issues/1818,
https://github.com/travis-ci/travis-ci/issues/5473,
https://github.com/travis-ci/travis-ci/issues/6671), it gets closed by
a Travis employee who thinks that FreeBSD is a Linux distro.

One overachiever managed to trick Travis into running FreeBSD by using
QEMU to fire up a VM as an unprivileged user process and run his tests
inside of that.
https://erouault.blogspot.com/2016/09/running-freebsd-in-travis-ci.html

And a few projects are even doing this very thing, though it seems
like a bit abusive to me.
https://travis-ci.org/rust-lang/libc/jobs/203950308


So my question is, what's the best alternative?

BuildBot can run on pretty much anything, and supposedly it can hook
into all of the popular code hosting platforms.
https://docs.buildbot.net/latest/manual/cfg-wwwhooks.html

Bamboo is also very portable, and has a slick GUI to connect to
Bitbucket.  Unfortunately, it's closed-source, but free licenses are
available for open-source developers.  Unfortunately, it's written in
Java.
https://developer.atlassian.com/blog/2016/02/totw-connecting-bamboo-and-bitbucket-cloud/

Jenkins is free and portable and has some level of Github and
Bitbucket integration.  Unfortunately it's also written in Java.
https://jenkins.io/solutions/github/


Does anybody have experience with any of these solutions?  Are there
alternatives I've overlooked?

-Alan