Is this regulation still applicable?
Can be found in SA regulations from 2006 and LH regulations 2009 (hopefully no longer the case).
It is not in fare rules unlike some other restrictions (ie sale in Venezuela etc), so i guess not a current restriction anymore.
IATA Resolution 024c, Section C: the acceptance of tickets
issued outside Mozambique is prohibited for journeys
commencing in Mozambique. The issuance of tickets in
Mozambique is prohibited for journeys commencing outside
Mozambique (6.4.93).