Yossarian,
The "2005 Act" was a revision of the 1989 act which was enacted as a result of Council Directive 89/391/EEC. A previous report in 1984 "Barrington Report" had identified a need for such legislation. As with most Irish legislation there is a historical context which has its roots in British rule of Ireland. British case law is relevant in Irish Courts and while is does not create precedent it is often referred to. Current drafting of Irish legislation is mostly comparable with the British equivalent. However similarities in legislation is most likely to be due to the directives of the EU. In recent years this appears to be changing as Ireland has introduced legislation which is not in place in Britain.

In reference to your particular question i believe the reason for this inclusion goes back to the 1989 act where the employer and self employed person we identified as different sectors. The 2005 act treats all employers as being equal with regard to their responsibilities. I am not sure that this is the exact rationale but might be some explanation towards it.
Kevin

The only exemption from the 2005 act for self employed persons is section 20 the requirement to prepare a safety statement. This exemption only exists if there is an approved code of practice for the undertaking, the person is self employed or has less than 3 employees and can document how they meet the requirements of the approved code of practice.