According to the koala tag wiki it is targeting questions about the Ruby-on-Rails koala gem. It has 169 questions
I am the developer behind the new Koala language to which is referred earlier (http://blog.camilstaps.nl/2012/11/koala-announcement/) As you can read there, this will be a language which can be used to program PIC microcontrollers.
However, this language will not reach a giant audience. For example, have a look at the - lower profile, in my opinion - Jal language, which has the same purpose.
I will take care myself for a discussion group on Yahoo or something to help people with problems. For a smaller language, that's easier than this - great though - website.
Therefore, I do not see it necessary to reserve the Koala tag. By the way, if my language will gain territory and this site would become useful to my users, the pic-koala tag could be used.
It seems there is a programming language called Koala, but it is not so extensively used to cause any tag clash, though.