Zivilgesellschaft is civil society. We're also dealing with a contrast between zivilgesellschaftliche Akteure, established political institutions and research institutions. Akteure is usually translated as "players." But I think we'd have to go with major or key players here.

"Civil society or civil institutions refers to the totality of voluntary civic and social organizations or institutions which form the basis of a functioning society as opposed to the force backed structures of a state (regardless of that state's political system).
While there are myriad definitions of civil society, the London School of Economics Centre for Civil Society working definition is illustrative:
Civil society refers to the arena of uncoerced collective action around shared interests, purposes and values. In theory, its institutional forms are distinct from those of the state, family and market, though in practice, the boundaries between state, civil society, family and market are often complex, blurred and negotiated. Civil society commonly embraces a diversity of spaces, actors and institutional forms, varying in their degree of formality, autonomy and power. Civil societies are often populated by organisations such as registered charities, development non-governmental organisations, community groups, women's organisations, faith-based organisations, professional associations, trade unions, self-help groups, social movements, business associations, coalitions and advocacy groups.
http://en.wikipedia.org/wiki/Civil_society