Indeed, you should expect the latest release branch to be available only for those packages that are officially supported.
For other packages, the main branch (which translates from the cvs HEAD) , is the place where the latest code is found.
The *-compat and other tags are translated from cvs and they refer to the OpenACS convention explained at https://openacs.org/doc/cvs-guidelines.html
Keep in mind that the oacs-5-10 branch is currently used as development branch, hence you should expect bleeding edge code from there now. For a more stable codebase you may prefer to stick with one of the release tags.
Hope this helps
Antonio
