A new version will be released soon

On May 17, 2012 Bing announced that version 1.0 of their Search API (a fundamental service used by BootCaT) will be decommissioned on August 1, 2012. This means that the current version of BootCaT will stop working on that day.

Moreover, Bing is no longer allowing users to register for version 1 of the Bing Search API, this means that, while existing AppIds will continue working until August 1, new users will not be able to obtain an AppId and therefore will not be able to use BootCaT.

The Bing API 2.0 will be supported by the new version of BootCaT, which is scheduled to be released in the summer of 2012.

Summing up:

if you have an AppId you should be able to continue using it until August 1, 2012

if you don't have an AppId, you won't be able to get one that is compatible with BootCat, there are only two things you can do:

borrow an AppId from someone else

wait for the next version of BootCaT to be released