because you already had some wxGTK, and maybe when you installed rc8 you did not have any...
about the mdk support, this is due to the fact taht teh guy from teh dev team who made those mdk rpms, left us some time ago, and since then we dont offically have mdk rpms anymore.
teh wardevil once are teh "unoffical" once, but tehy have been shown to work very good, just also dl his wxGTK rpms and his amule version
tata