Responding to a tweet from @falco_girgis (one of the individuals who is contributing to the fanmade port), Vermeij said, "There is an impressive effort going on to make gta3 run on the Sega Dreamcast. The first months of development of gta3 (back in 99/00) were done on the Dreamcast. For commercial reasons we switched to ps2. At the time we did think it was technically possible to pull it off on the DC and these guys are actually doing it. Nice one."
In case, you're not up to speed with your GTA history, the development of GTA III was born out of a Godzilla-based 3D project that Leslie Benzies and a group of Space Station Silicon Valley developers were working on after finishing the N64 platformer for the Sega Dreamcast.
Eventually, after Take-Two bought DMA Design in September 1999, the idea for the Kaiju project was dropped and a decision was made in favour of consolidating the GTA 2 and Space Station Silicon Valley teams into a single development group, to bring GTA III into 3D on the Sega console. Work was done on the platform for a small number of months, with the precise amount of progress being up for debate, depending on who you ask. But then, as Vermeij mentions, the decision was made to drop Dreamcast as the main development console and move work over to the PlayStation 2.
It's amazing to see Vermeij highlight the project in this way, and it's clear from his comments that he has an appreciation for the work that has gone into it so far. When asked by a random Twitter user why someone would even want to port GTA III to Dreamcast all these years later, he issued a defense of the project, responding with the famous quote, "Why climb the mountain? Because it's there."