Default Locked bootloader AOSP

Since my Xperia Z just won't unlock again I'm wondering if theres an AOSP for locked bootloaders?
Xperia X8 - stock 2.1 / rooted / unlocked
Xperia Z - stock 4.3 (10.4.1.B.0.101) / not rooted / locked
Nexus 7 (2012) - miui v6 / rooted / un-locked