I currently work in Libya and spend approximately 6-7 months in the country and return to my home in the Netherlands on my time off. I do not work in Holland nor do I have a Dutch employer. I am an Irish national and hold temporary residency. My house and family - wife and two children are in the Netherlands. As I spend more than 6 months of the year outside of Holland, with my income earned abroad through a foreign company, am I liable for income tax?
Since you are living in the Netherlands you will have to declare your world wide income in your Dutch tax return. This includes the income earned in Libya. The Netherlands don‘t have a tax treaty with Libya. In that case the Decree to prevent double taxation becomes applicable. This decree will arrange that (double) taxation in the Netherlands can be prevented for the income from Libya if you are also taxable in Libya on this income.
The fact that you are in Libya more than 6 months per year is not relevant. Your main residence remains the Netherlands, since your wife and children stay in the Netherlands and you have a house here.