Is internet radio really radio?

Technically speaking, no.  Here is how radio is defined in the dictionary:

ra⋅di⋅o

[rey-dee-oh]
-noun
1. wireless telegraphy or telephony: speeches broadcast by radio.
2. an apparatus for receiving or transmitting radio broadcasts.
3. a message transmitted by radio.

Therefore, the internet, something relying on wired connections for the transmission of data for the most part, is not radio.  A radio station that is streaming audio, is a different matter.

Aside from that technicality, there is something else that is important to note.  Internet broadcasters (AKA webcaster) lack some other key components that make a radio station a radio station;  A specific set of rules that govern their behavior.  Things like profanity, copyright infringement, slander, payola, plugola, syndication rights, advertising rules (things tobacco, alcohol) emergency information, public issues and so on.

A radio station license is granted in the public interest.  Time was that radio station were required to do a certain amount of public service broadcasting, things like the news, religious programs, community interest programs.  Many station still do this.  An internet broadcaster is under so such constraints.   Some would say that is better and it just might be.  However, when Tim Westergren says “don’t call it internet radio, just call it radio,” sir, you are wrong.