While the information on this site currently remains available for reference purposes, you are strongly recommended to use at least the latest MariaDB release in your series. You can download packages and set up repos from http://downloads.mariadb.org/. For more information see the summary post MariaDB Security Updates or ask Open Query.
For MySQL 5.0 we do two builds, ourdelta (standard) and ourdelta-sail (bleeding edge) where the latter contains newer patches that may not (yet) be stable. The dN indicator (e.g., d7) shows from which patchset build the feature is included. For MariaDB 5.1, there’s only an ourdelta build, Monty intends 5.2 to be the more bleeding edge tree.
If you see a certain patch not yet available for a version of MySQL, that means you have an opportunity to contribute: you port it, we build it! See the OurDelta project on Launchpad, where you can also find the individual patches and other support files we use. Everything we do is all open and public. You can join the OurDelta-developers team which also has a mailing list, and bug tracking.
We provide proper repositories so you can simply add us to your favourite package manager! If you need to build from source (for instance, for a platform we don’t handle), we also provide source tarballs incorporating our patches (we generate this once per build and feed it into the build systems), and generic binary tarballs for Linux. The repositories also contain source packages wrapped in the format appropriate for each distro.