Question about jailbreak and app in development stages

[jigga18]

i have an iphone 3gs with 4.3.5 ios,
I tried to install a custom app thats in its design stages to test it out. When I tried to sync it in itunes I kept getting an error saying: "the signer is not valid"
So I jailbroke my phone and tried it again and I still got the same error.

Do I have to purchase a developer account in order to test the app?

[Orby]

i have an iphone 3gs with 4.3.5 ios,
I tried to install a custom app thats in its design stages to test it out. When I tried to sync it in itunes I kept getting an error saying: "the signer is not valid"
So I jailbroke my phone and tried it again and I still got the same error.

Do I have to purchase a developer account in order to test the app?

Assuming this app is from a legitimate Apple developer: ask them to check the validity of their code signature certificates, make sure you have the correct intermediate certificates installed in your keychain, and make sure the app is signed. If it's an ad hoc distribution, make sure you have the correctly signed provisioning profile. While you shouldn't technically have to be a developer, you will need the correct certificates.