Version 9 was released with GMod update 95. Here is the full changelog:

New features

• Weapon switching menu is more configurable. In the Settings tab of your F1 menu, you now find an option for making the menu never auto-close, and an option for the "fast weapon switch" that also exists in other Source games.
• HUD-based Traitor buttons allow traitors to interact with the map without anyone seeing them. When playing on Zombie Master maps, the manipulates are now controlled by these buttons. See "mapping" section below for more information.
• DNA Scanner now continues recharging and auto-scanning even while holstered.
• Newton Launcher now has a secondary charge-up firing mode allowing you to fine-tune how far it pushes your target.
• Quickchat messages ("I'm with X" etc) now count as someone's Last Words if they were sent just before death.
• Experimental silly hat for detectives on certain playermodels (phoenix and arctic). Servers can disable with ttt_detective_hats 0.

Balance

• Headshot damage multiplier reduced for the HUGE and MAC10, and significantly increased for the UMP.
• UMP view punching is now stronger.
• Newton Launcher sound is less obvious and has a much shorter range in which you can hear it.
• Disguised Traitors will not appear on a Detective's radar. They will still show on fellow Traitor radars.
• C4's penalty for a wrong disarm code is now much higher at longer fuse times. The penalty is shown in the arming screen.

Fixes

• Fixed clientside NPC ragdolls not being cleaned up when a new round starts.
• Fixed rare Lua error in weapon HUD drawing code.
• Fixed traitor voice indicator colour flickering.
• Fixed damage log reporting values that were too high in certain specific cases.
• Fixed C4 wrong disarm code time penalty always being 1 second.
• Fixed "switch to previous weapon" (lastinv) command not working right with the Holstered weapon.
• Fixed spectator "living player" muting remaining active while you're alive if you turned it on just when a new round starts.
• Fixed issue on Linux servers where the DNA scanner menu would error.
• Spectator pressing USE on a player will now properly spectate that player instead of pseudo-possessing him.
• Tweaked text of certain awards and their likelihood of appearing in the highlight listing.

Mapping

• New entity: ttt_traitor_button. This is a button only visible to Traitors, shown on their HUD, from which they also press it. Allows you to have easy traitor-only buttons without having to protect them from innocents.
• New entity: ttt_damageowner. Allows you to make an entity's damage and kills be attributed to a player. Meant for making traps and such give points to the player that enabled them. They will also get reported properly in the round report instead of "Bob was killed by something". Instead it will be "Bob was crushed/fried/exploded by Joe using <name you specify>".
• The mapping guide has been updated with information on these entities and an example map.

Modding

• Headshot damage multiplier is now defined in each SWEP, allowing custom weapons to mess with it.

Server and admin stuff

• Almost all of the gamemode's stuff is now in /gamemodes/terrortown/content/. GMod automatically loads it from that location, so not much should change. You should put all your maps and custom content in the same place you've always been putting it. For FastDL, you may want to copy all the stuff in /content/ into the main garrysmod directory, though in practice no one will have to download that stuff anyway.
• The first round after a map load now has a longer preparation phase by default so more people can spawn. Customizable via ttt_firstpreptime.
• Use of ttt_print_traitors and similar commands is now logged to the console.
• The ttt_print_damagelog can now be used by all players during the post-round phase (note that for the command to work at all, ttt_log_damage_for_console must be 1).