The remedy for open code inclusion into closed code is roughly the same remedy sought for closed code inclusion into other closed code. Copyright law serves the creators of open code as well as it does closed code. In this, the remedy is clear; either remove the offending code, or modify the license of the entire code body, or seek alternative licensing with the owners of the code.
http://linuxtoday.com/news_story.php3?ltsn=2004-10-25-024-26-OP-SW