in march 2003, sco filed suit against ibm alleging that ibm's contributions to various free software, including fsf's gnu, violated sco's rights. while fsf was never a party to the lawsuit, fsf was subpoenaed on november 5, 2003. during 2003 and 2004, fsf put substantial advocacy effort into responding to the lawsuit and quelling its negative impact on the adoption and promotion of free software.