If there is a bit of techsing grandmother to suck eggs in this, tough.
Open source software allows other people to use and modify the code for their own purposes. The usual licence under which you can do this includes a statement that your modified version of the code is also to be open source (and therefore made available to others) and that the code cannot usually be used for commercial gain (even if it is modified).
Black Duck seems to be a set of software tools which will search your code for open source software, check the licence and flag it up if you, as a commercial developer, are including any in your application.
That doesn't stop you using open source code, but you might have to check the licence terms, get permission from the author(s) to use that code, make the modified version available under the same terms as the original licence and include an acknowledgement in your own documentation that you are using one or more pieces of open source code in your application.
Given the complexity of some applications, doing the checking manually could get to be a bit of a pain, so the Black Duck software does it for you, and will also notify you if any of the open source code you are using has known security vulnerabilities.
I'd guess that it searches source code rather than object, and won't flag up snippets but would pick up on a substantial chunk of code from an open source application. for more technical stuff, you'd have to find the right person to talk to at Black Duck.