Split supersymmetry allows gauge coupling unification as supersymmetry does, because the particles which have masses way beyond the TeV scale play no major role in the unification. These particles are the gravitino - which has a small coupling (of order of the gravitational interaction) to the other particles, and the scalar partners to the standard model fermions - namely, squarks and sleptons. The latter move the beta-functions of all gauge couplings together, and do not influence their unification, because in the grand unification theory they form a full SU(5) multiplet, just like a complete generation of particles.