Yep, and honestly it's going to come up with things other than lawsuits.

I've worked at a company that was asked as part of a merger to scan for code copied from open source. That ended up being a major issue for the merger. People had copied various C headers around in odd places, and indeed stolen an odd bit of telnet code. We had to go clean it up.

Headers are normally fine. GPL license recognises that you might need them to read binary files.