No idea where you got your info from, but I do know it is wrong. In TX you have to hold a valid state hunting license to catch non-game species, including: amphibians, turtles, lizards and snakes (there is no distinction between venomous and non-venomous). Last year possession limits were 25 total animals (dead or alive), no more than 10 of a single species. I'm not sure if it has changed for this year or not, I haven't been out.
Protected species may not be taken at any time - included (but certainly not limited to) in those species is the Louisiana Pine snake, the Canebrake Rattler, the Texas Tortoise (the only tortoise species native to TX), and the Indigo Snake.
My guess is that the snake you have is a bullsnake, they are by far the most common Pituophis in TX... but if it is a Louisiana Pine, you best not let Parks & Wildlife know you have it.
Ham