"...people working in the Netherlands will normally be exempt from paying tax on their income earned there if they are physically present in the Netherlands for less than 184 days in a twelve month period or tax year and if they are paid by a non-Dutch employer. "
Sounds sensible to me anyhow!
But it's certainly a complex area and anyone thinking of taking an EU contract should seek professional and legal advise from all the parties involved to establish everyone's liability and fully converse with the local tax authorities before signing anything. This is what all 5 parties in my chain did anyhow.
In a way the guy who started this thread won't get much comfort from reading anything on here as it's not professional & legal advise for his specific circumstance.
But it's nice to swap indivdual examples.