The speculation amongst the Internet is that this may signal a move to injured reserve for DE Mario Williams who is suffering from a sports hernia.
Green 31, was released from the Broncos in September after signing a four-year extension in the offseason. Chalk it up to another brilliant Josh McDaniels move. Green also played in New England where he had a career-high 7.5 sacks in 2006.
For Green to join the roster officially, the Texans do need to make a roster move of some sort so be sure to check back with SB Nation Houston and Battle Red Blog for more as the story develops.
EDIT: Name correction, I meant to type Jarvis Green not Jarvis Moss. Apologies for the error.