Does BluBracket store/modify my code or any part of my code?

The simple answer here is NO. 

During the initial scan of the repositories to be monitored, BluBracket clones the repositories, scans them, creates a hash of each of the files (for later comparisons), and then deletes the repositories from the BluBracket servers.  All of this happens within a few seconds depending on the repository size.  BluBracket then saves specific metadata for easy reference - things like repository names, file names, contributor IDs, commit IDs and times, etc.  BluBracket does not modify or store any actual code or secrets found in code on their servers.