Heres your full description:
Once upon a time Blockland was a much much worse but free version, when playing people wanted to have certain things, so they modded them in. A mod called TBM was made and ran by several people, and then RTB was too. RTB and TBM added new things to Blockland, they ran from seperate .exes. TBM included a exploit which the creators admitted to, so Badspot banned it from the forums and RTB became the only BIG mod. Anyway no RTB is not a add-on for Retail, it is a mod for free Blockland.