To cover the operating costs, pay their employees, etc. If they gave them away free they'd need sponsors I guess.
So it's probably to maintain neutrality.
So it's probably to maintain neutrality.
Does that mean submitters and downloaders pay or just downloaders?
From your link (2011):
55 % through membership fees
45 % through sales of publications and other income from services
2010: 53/47
2009: 55/45
2008: 60/40
..
2006: 62/38
2005: 65/35
..
2002: 80 % - financed directly
20 % - member body subscriptions and publications income
I think they can operate without paid publications. They could, at least.