Currently, the essential document for implementation of the Open Science idea is Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities, which builds on previous initiatives (both from 2003):

Budapest Open Access Initiative

Bethesda Statement on Open Access Publishing

These three documents are called, in summary, Open Access BBB initiatives.

Berlin declaration was accepted in October 2003 at the conference organized by Max Planck Society in Berlin. Declaration builds on both previous documents and defines principles and methods of implementation of Open Access. The Berlin declaration was signed on the 20th of February, 2015, by 497 institutions worldwide. Masaryk University was the first university to access this initiative (on the 11th of October, 2010).