Oral sex was considered sodomy under Texas state law, along with anal sex, for same-sex couples. But the law was struck down by the US Supreme Court in November 2003, by their ruling in Lawrence and Garner v. Texas. My guess is that the use of the term "sodomize" in reference to oral sex is cultural rather than legal. It's interesting though, that the article says Nix was indicted for "sodomy and assault". Strange, given that Texas sodomy laws only referred to same-sex encounters. I'm stumped.