If you want to release your application on Cydia, you must fake code-sign so that every device can use it without problems.
First thing first, Things you will need -->
Both can be downloaded from Cydia.
-- Go To /Developer/Platforms/iPhoneOS.platform/Developer/SDK/THE_SDK_VERSION_YOU_ARE_USING/
-- Then copy SDKSettings.plist to somewhere to edit
-- Open that plist and under Default Properties, change the following
CODE_SIGNING_REQUIRED to NO -> then save it
-- Copy that plist and overwrite the original plist (you might need to enter yr mac password, etc)
-- Open up yr xcode project
-- Go to Project Settings, under code signing - change Code Signing Identiy - Any iOS to Don't Code Sign (image: http://d.pr/y3Uw) and then just* Build (NOT Build and Run)
-- If you did every step correctly, you would be able to build without errors
-- then find your package your package should look like this (image: http://d.pr/zdkX)
-- Copy that file to your iDevice, open up mobileTerminal and enter the following lines
cd your_package_dir/your_package.app (for example: if your package is example.app which is inside /var, type cd /var/example.app)
chmod 755 your_package (changing yr_package binary permission to 755)
ldid -S your_package
After that you may see the errors like
util/ldid.cpp(582): _assert(0:WEXITSTATUS(status) == 0)
which is not a problem.
Then respring your device and you get the fake code sign package.
That's about it. I hope it helps you in some ways. If you aren't clear about something, leave a comment.