"#3 pencils and quadrille pads." - Seymoure Cray (1925-1996) when asked what CAD tools he used to design the Cray I supercomputer; he also recommended using the back side of the pages so that the lines were not so dominant.
AdriPSX has been programmed by the same person all since it's first release back in 1999 - by Roor. A guy running the website Emutech2k (also an emulation related website) convinved Roor one day to start an emu and publish it. Fast progress was being made and the first game ran soon afterards.
Then, Emutech2k closed it's doors and AdriPSX moved over to PSXEmu (NGEmu today). After Zico give the site a new design, progress was also being made. Today, AdriPSX is one of the fastest PSX emus out there and certainly belongs to the top when it goes to compatibility.