And what's the problem?

The problem I had was with another program which is waiting for selenium to complete
its startup process, and was reading from stdout to determine that it had. 

Although the program could be modified to read from standard error as well, I'd argue
that it's unexpected that selenium's startup messages, none of which are errors, are
sent to standard error instead of standard out.

There are no special "startup messages", it is just a part of the log. Selenium server
is a server, and for this reason it should not write to stdout. Nobody expects e.g.
Apache web server to write something to stdout.

Why older versions wrote something to the stdout? Because a bug :) And it was fixed.

By the way, instead of watching the log your program would better poll the ability
to set network connection to the selenium server.

Thanks, good point regarding apache. And thank you for the suggestion, I will use polling
instead.

While I do understand that you do not want to write to stdout because it's a server,
what's the point of writing INFO messages to ERROR output?

You better not write anything at all in this case. Even if it's not a good decision.

Please I am a UNIX noob, do you have a reference page stating that no server should
write to stdout? Thanks.