If I wanted to clone the Roller Coaster Tycoon engine...

...what would you say my easiest path would be? best path?

Does anybody here have experience playing around with the guts of OpenTTD?

Nevemrind.

Found OpenRCT2 after a 3 second google search.

But I heard you on that browser thing!

GitHub - OpenRCT2/OpenRCT2: An open source re-implementation of RollerCoaster Tycoon 2.