Well, we definitely have to write a custom solution for our clients, so probably not. Though I will say that our data sources are probably the same.
ALL of the required data is 100% FREE, and comes from the US Govt. It comes in a (very big) set which is a compilation of Census, Postal Service, USGS, NOAA, USCGS and other divisions' data. Many map makers either sell that data with no changes, or add certain waypoint data (like every Denny's, various hotels, etc - chances are making money from both ends... including businesses, and charging for the maps), or correct certain features (for instance, though I have the data for each clover-leaf exit on a highway; they may correct the paths on major ones to actually look like the real thing for the odd shaped ones).
To compare, I use GPSU (win16) version instead, so this is what you are 'up against'.

In GPSU i.e you can 'calibrate' your track on top of just about any bitmap, for future reference.
Underlaying a bitmap is easy. Even getting the bitmap images (like the one he scanned in for one of the maps on his page) is also easy... but currently the easiest way to get them is in PDF form - and the PDFs are massive. Compressed, they total over 50GB, and each represent a 24"x32" map (or 32"x32" or 24"x36"... you get the idea). While it is easy enough to convert them all to bitmaps (or some similar format) the outcome (in file size) is massive. After that, the maps need to have corner points set (longitude and latitude points) so that they correspond to what streets or routes are being drawn. In addition, the extraneous space needs to be removed (the map borders and map legend, etc).
Now, there are other sources of image data that can be used as well (which are also free - or low cost), which could produce results akin to Google Maps' hybrid satellite/mapping mode. But those are things we will look into in the future - even without such things, we can at least draw many topographical features (such as mountains, rivers, etc) with high accuracy. The data we have is accurate to within 6 decimal places longitude or latitude (pretty darn accurate). One of the version will probably include the ability to link images to certain areas so that industrious people can import their own backgrounds.
As for street drawing, currently, our maps will look somewhat similar to his... and eventually look a little more similar to Google's Maps. Inotherwords, (in the first version) a highway may be drawn with one single 4 pixel line, a road with 1 single 1 pixel line, etc... and in the "more advanced" version, a highway would be drawn with 2 lines 6 pixels apart, while a road is drawn with 2 lines 1 pixel apart (so that it appears you are seeing the edges of the road instead of just the centerline of it).