For multi-configuration projects, links to FindBugs results won't be added to the project page. There also are no links on the build pages (the one you reach by clicking a link in "Build history" on the project page) and the pages on the configuration.
The FindBugs results can however be found on the build pages for the configurations (can be reached by clicking on a build in "Build history", then on a configuration).
Since in my case the FindBugs results should be identical over all configurations, I expected to find a link on the main project page, as it works with other project types. At least I would have expected to find a link on the configuration pages, not only the configuration pages for specific builds.