The WWW Server versions Elsjeu, Kerstvers, Verwerking, Roepvooruit and Compieuw share the same format of the file www.ini. Therefore, it can be exchanged between servers of these versions without any problems.
The Raai series has introduced a new format. It is no problem to leave a www.ini file from Compieuw or below when you upgrade to Raai, as it will be automatically converted to the new format.
The reverse is not possible, though. When you try to use a new format ini file with the Compieuw series or below, the server will most likely just discard it and do as if it were not there. Older versions may also crash, though.