In DGL at least its not allowed.
http://gaming.do.co.za/helpdesk/index.php?/Knowledgebase/Article/View/59/28/general-league-rules
Cheating and violations
Cheating is any unlawful measure that gives a player an unfair advantage over others. Such measures include (but are not necessarily limited to):
3rd-party software (which may/may not be integrated into the game code) which bypasses the natural competitive mechanisms of the game.
Where the game provides such an interface, scripts/macros (known as “bindsâ€) which would not otherwise be possible to execute or provide an unfair advantage.
Exploits (including game engine exploits, video driver setting exploits (Ambient occlusion/LOD), modification exploits and map exploits).
Players should use default player models, weapons skins, heads-up display (HUD), point-of-view (POV), and sounds. If a default/standard configuration is supplied, players must use this.
Use of restricted/unfair CVARs or DVARs.
Cheating can and will be monitored by the officials. They reserve the right to review game demos and make a collective decision on any or all of these infringements. DGL has the right to consult with the designated community watchdog regarding any hacking disputes.