Drive [Q][DEV] Other OS's porting/ booting question thread

Hi all, I have some questions about porting other os to an Xperia (especially Xperia Mini Pro) android phone..

1) What is needed to boot an alternative OS on our phones, is the bootloader capable of running a OS from sd card or should I rewrite android?

2) Are there any closed source components that might be a problem in the adaptation of mer/sailfish for our phone?

Thank you very much.