Open access publication is free of charge and available for everyone
Open Access scientific publications must be open for reading and evaluation to researchers and the general public alike free of charge, if not immediately, at least after an embargo period. Many publishers continue to require an embargo period (usually 6-12 months), during which the article is only available to the paying subscribers of the journal.
European Commission recommends, that there should be open access to publications resulting from publicly funded research. http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32012H0417&;rid=1
Horizon 2020, the EU Research and Innovation
programme http://http://ec.europa.eu/research/participants/data/ref/h2020/grants_manual/hi/oa_pilot/h2020-hi-oa-pilot-guide_en.pdf, requires that under Horizon 2020, each beneficiary must ensure open access to all peer-reviewed scientific publications relating to its results no later than no later than 6 months after the date of publication, and 12 months for social sciences and humanities , Model Grant Agreement for Horizon 2020, article 29.2. Each beneficiary must ensure open access (free of charge, online access for any user) to all peer-reviewed scientific publications relating to its results according to H2020 General Model Grant Agreement http://ec.europa.eu/research/participants/data/ref/h2020/mga/gga/h2020-mga-gga-multi_en.pdf.
Enablers and barriers to Open science have been described in more detail in the publication Science 2.0, Science in Transition, released by the European Commission in February 2015, http://http://ec.europa.eu/research/consultations/science-2.0/science_2_0_final_report.pdf#view=fit&pagemode=none.