  In this short note we present a mathematical interpretation of tachyon
condensation on (three dimensional) orbifolds within the framework of boundary
string field theory (BSFT). We explicitly show that important parts of decay
modes in brane-antibrane systems with N=2 boundary supersymmetry can be
interpreted as the McKay correspondence described as complexes. This will give
an example of the recent interpretation of D-branes as derived category. We
also discuss the N=4 boundary supersymmetry as a more refined structure.
