I'm not sure that I would say that Wilbur isn't being developed. It's quite likely that there's been a fair amount of development, just not any public releases for a while. As I understand it, there's just the one developer who is currently working multiple jobs and has small children, leaving little time for Wilbur development (plus, he's getting on in years). Plus, the total revenue-generating properties of the software have been negative for a very long time.

The last update that I had heard about involved turning the entire system inside-out to allow for automated processing (effectively macro record and playback). Wilbur's code base dates back to 1995, which makes it plenty old enough to vote in US elections, but not quite old enough to drink at a bar. There were a number of issues relating to the code even back then and there has been a comparatively huge amount of work done over the last 20 years to keep things going.

A few years back, there were discussions about doing a version of Wilbur that supports tiled surfaces, but the changes needed in the code base were quite extensive and the expected performance properties were pretty poor.