source: http://opensvn.wiimm.de/wii/trunk/wiimms-iso-tools/
yes, you are allowed to build it yourself (exact licence terms in gpl-2.0.txt)
signing should be ok too
but afaik apple does not allow open source programs on its app store
edit: apple has a problem with copyleft not open source
copyleft licences such as the GPL require you to give certain rights to your customer
e.g. you would need to grant him the right to distribute/modify the program
apples terms of service aparently do not allow you to grant those rights
see http://www.fsf.org/blogs/licensing/more-about-the-app-store-gpl-enforcement
yes, you are allowed to build it yourself (exact licence terms in gpl-2.0.txt)
signing should be ok too
but afaik apple does not allow open source programs on its app store
edit: apple has a problem with copyleft not open source
copyleft licences such as the GPL require you to give certain rights to your customer
e.g. you would need to grant him the right to distribute/modify the program
apples terms of service aparently do not allow you to grant those rights
see http://www.fsf.org/blogs/licensing/more-about-the-app-store-gpl-enforcement