Does Unlocking bootloader affect network lock? Will the bootloader unlock procedure as shown on the HTC Dev website affect my network lock? 

I have an HTC Aria, which was originally SIM locked, but I got unlocked from a shop. Now, since I'm working on Android apps and HTC devices, I want to unlock my bootloader, but I'm worried that it will re-lock my device to the original carrier.
No, the bootloader has no bearing on a SIM/network lock. The HTCdev site explicitly states this on the bootloader unlock page, in fact:


  Please note that unlocking your bootloader does not mean that you will
  be able to unlock the SIM lock. Unlocking your SIM lock is at the
  discretion of your operator/carrier and is not part of the bootloader
  unlocking scope.


The reverse is also true, but the main point is that the two concepts are unrelated.