ahaa...this is where your got the first strikes (two more left)...you need to own a symbian^3 phone to understand the behavior of this system...
if you wanna know 98% of all apps on symbian is not free & 100% of them need a certificates if you want to install it...only a hacked/modded symbian system can install apps without having a certificates but still those apps need to be cracked first...
how to hacked/modded symbian??? well you need to own one symbian phone first....you need to test your hacked/modded symbian before you can try to port it on our beloved N900...
why you need to test hacked/modded symbian??? you needed because hacked/modded symbian is much better than the unhacked/modded symbian...try porting the unhacked/modded symbian to N900 will be a disaster for you....