This is the official page of the a0poster-isc07 LaTeX class.
Since a0poster-isc07.cls is free software, you can download, use, modify and redistribute it to your heart's content, with some caveats (see license). If you would like to share your corrections/additions with me, I'd gladly hear of them by e-mail.
a0poster-isc07.cls is a Derived Work from the file a0poster.cls, by Gerlinde Kettl and Matthias Weiser. The latter file is part of the standard LaTeX distribution, and you should be able to get it at the Comprehensive TeX Archive Network
This file is a class file for making DIN A0 sized posters. You should use it along with the standard a0size.sty file (that you have already installed, most surely). You can see a sample poster here.