  If strange quark matter (SQM) is the true ground state of hadronic matter,
then conversion of neutron stars (NS) into quark stars (QS) could release some
10^{53} erg. We describe a scenario of burning of a NS into a hot,
differentially rotating QS. Emission of released non-baryonic energy through
the QS surface is discussed. The role of magnetobuoyancy of SQM is mentioned.
The outflow of gamma e+ e- lasting for up to ~1000 s could be at the origin of
long GRBs. Advantages of hot, differentially rotating QS as an inner engine of
long GRBs are reviewed.
