not quite. The gnutella vendors agreed upon a standard hash to use for URNs and that was SHA-1. Shareaza however wanted to use bitprint URNs, so they started using different magnet links.

Both of them are URNs. Shareaza just uses an additional TigerTree hash that LimeWire does not support in magnets.

Besides, LimeWire does not support query by hash anymore, so even if LimeWire read Shareaza's bitprint urns (which it could do easily) it wouldn't be able to search for the files by urn.

Queries by urn were banned because they were causing to much traffic. Agressive servents such as XoloX, Phex or Mutella were sending requeries far too often (Mutella was sending a requery every 60 seconds for each file it was downloading).