Snyder was the guy who put the foot in the doorway; but the early parts of that otfans wiki is correct. You can thank Jakexblaster for the first map editor.
...I can't remember the first server with real multilevel...but I think BlackDemon coded it, as far as I know he was also the first one who had functioning houses in his server.
As far as I remember, Haktivex had his own private Tibia server, where the Del'Toros used to practice their PvP skills, I used to play there, then I was introduced to Fandora and got to know TDA and later OTServ.
Unfortunately I am part of the problem with TDA, Fandora gave me the map editor and the source, I worked on my own server and a friend of mine asked for it, I gave him, he leaked it (remember the same map with the God being a Fire Elemental? Yea, I still have it somewhere in a Floppy, but I don't have floppy drives anymore).
Jakexblaster coded the SECOND map editor, the first with multi-levels. And distributed the code to make your server work with multi-levels, I made it work on mine.
Back then, Tibia 7.1 servers had no stackables, no save, no house system. Me and Vitor started coding save systems, house systems and stackables. But in the meantime, OTServ team was working on 7.4-7.6 already and the stackables system (for them) was already working.
Just for the record, Haktivex's server:
Experimenting monsters IA