One of the inescapable facts of free software is that it involves a lot of law - far more than innocent hackers might expect when they settle down for a light bit of coding.

[…] The problem is that even a tiny licence fee, if levied on a per-copy basis, is impossible for free software because of the way it is distributed. There is simply no way to know how many copies may be shared, and hence no way to collect all those eminently reasonable and non-discriminatory licence fees.