wetware: spirit_66 has said it too: Playing against bots I can do this on my PC with GNU, Jellyfish whatever for free.
The reason I asked you what you meant is that I think that argument rather misses the point. The point is that someone is masquerading bot as a person not that they are providing a bot to play against.
With regard to that latter point, whenever a site provides a bot to play against it is well attended! You may well have GnuBg at home but you cannot play turn-based against it with anything like the ease that you can at a site designed for the purpose. gb001, one of Dailygammon's GnuBg-based bots is very popular and not just with those who don't have GnuBg themselves. ;-)