Apple is sending out invites to random registered developers, giving them the chance to buy an Apple Watch with guaranteed delivery by the end of the month. Developer get the opportunity to buy a 42 mm Apple Watch Sport with shipment by the 28th of April. Apple is emailing selected developers, who are offered to apply here.
The process is by application only. Developers find out whether they are eligible to actually go through with the purchase on the 23rd of April, this Thursday.