I suspect there isn't much money to be made in online backgammon though, which is why it hasn't been cracked down upon. About saying you have to use a second PC, O' talking about it in the sense that bots are already run these days. Poker sites will scan for bots in your computer's memory (which is illegal btw, but they don't care and it is a good thing). That is why you have to run your poker bot on another computer which controls the client PC with the poker software through remote desktop. Anything your eyes can see can also be interpreted by a computer, so poker sites cannot ever hope to prevent bots from running their software. Only make it exceedingly difficult.

An old colleague of mine for example made a program that instantly solves minesweeper. All you see is basically the mouse going from bottom left to top right and bam even the biggest one is done. This is implemented through pattern recognition, an easier way is through packet sniffing or using API commands (such as being able to read a table's name which your HUD needs to distinguish your tables), this is most common but anything is possible, and if enough money is at stake someone will try to do it.