You've got copyright rights to use it, but that doesn't mean you have patent rights to use it. This is true of BSD licensed software in general, the author can

You've got copyright rights to use it, but that doesn't mean you have patent rights to use it. This is true of BSD licensed software in general, the author can grant the copyright to copy and use it because they own that, but there may be patents that cover the relevant area which they may not own and so they cannot grant a patent license. As far as I know the BSD license is not normally thought to contain an implicit grant of patents that the author holds. If companies thought that it did, they would probably set up separate companies to funnel all their open source contributions through so that there could be no misunderstanding about patent licenses. Regardless, if I thought I was depending on an implicit patent license that had never been tested in court for some important piece of software my company was using, I'd be more nervous than if that patent license were explicit.