CS 1.6 uses specific ports (usually port ). To bypass this, you need to make your traffic look like regular web browsing.
Valve has historically allowed community servers to thrive. They do not aggressively pursue emulators or browser ports because these versions often drive players toward the modern CS:GO (now Counter-Strike 2 ). As long as no one is selling the game for profit, the community is usually left alone. Counter Strike 1.6 Online Unblocked