about  www.m-bus.com

This website was set up way back in the time when the M-Bus scheme was developed and transformed into a European Standard.

The first standard was EN 1434, where in the parts -2 and -3 the M-Bus was established as the means of wire-bound communication for heat meters.

The next step was to include the M-Bus into the EN 13757 standard for communication systems for and remote reading of any type of meters.

Since this development has come to a successful end, all info needed can be found in these standards, so this website seemed superfluous.
However, there still is the documentation part, which gives some info about timeless M-Bus principles as well as the Buyer's Guide (which has been continuously updated) that seem to be an accepted source of information for many users and therefore will continue to be supported.
However, if you need detailed technical information about M-Bus communication, you'll have to turn to the printed standards.