SonarLint is an IDE extension that helps you detect and fix quality issues as you write code. Like a spell checker, SonarLint squiggles flaws so they can be fixed before committing code. In order to use it in Progress Developer Studio, you have to use a slightly modified version of the original SonarLint package, and install it using the usual Eclipse installation process.
Version 5.5 brings support of multi-location issues (core issue located on a specific keyword, and additional information related to this issue located on different parts of the code), support for the latest Eclipse versions (but still compatible with PDSOE 11.7), and support for the latest SonarQube 8 releases, better handling of the database connections and project structure. This version also contains sample rules (unused variables or whole index usage for example) which can be immediately used without having to enter the connected mode (where you can use the full set of commercial rules).
Source code of the SonarLint plugin is available here.
The modifications for Progress Developer Studio support are available here.