There haven't been any changes on this service in a long time. I couldn't even find the string "no-ip.com" or anything similar in any source file of m0n0wall.
Lennart I don't think Fred was refering to no-ip.com as one of the listed dynamic DNS servers. Looks like when he specifies a custom server such as dynupdate.no-ip.com, it looks like the string gets parsed down to no-ip.com.