Well... any solvent that be volatile enough (acetone, alcohol, isopropyl alcohol, etc) can be used for making hash oil, provided it be completly evaporated after the extraction.

The only problem are the impurities of the solvent. Many of them are not so volatile as the solvent itself, and may remain mixed with the hash oil even after the solvent is evaporated. Some of the impurities can be poisonous, and i think thats why some people says its dangerous.

Anyway, you can put some of the solvent you will use into a dish and evaporate it to see if some residue remains. If no residue remain, you can use the solvent without any worries.

And when evaporating the extracted solvent+thc, it must be evaporated as completly as possible (bone dry), to ensure all the solvent (that may be harmful) is gone and only the pure thc oil is left.