The FNRS rules stipulate that Â«seules les publications en version Ã©lectronique intÃ©grale gÃ©nÃ©rÃ©es sous format pdf Ã partir des dÃ©pÃ´ts institutionnels des universitÃ©s de la FÃ©dÃ©ration Wallonie-Bruxelles seront prises en considÃ©ration par le F.R.S.-FNRS et les fonds associÃ©s dans leurs procÃ©dures dâ€™Ã©valuation et dâ€™attribution de crÃ©dits de rechercheÂ» (Article 9).
The FNRS requires that you upload on DI-fusion, your final manuscript of the articles, after peer review, with revisions having been made. This is called the postprint. (The preprint is the version of the paper before peer review.) In terms of content, post-prints are the article as published. However, in terms of appearance this might not be the same as the published article, as publishers often reserve for themselves their own arrangement of type-setting and formatting. Typically, this means that the author cannot use the publisher-generated .pdf file, but must make their own .pdf version for submission to a repository.
The FNRS invites researchers to deposit the postprint version (but the publisher-generated pdf is ok also if permitted by the publisher!), as soon as possible after publication, and no later than 6 months after publication; this rule should be applied to future publications.
For previous publications (before July 2013), the FNRS invites you to deposit the articles published since 2008.
In order to know the open access policy of the publishers, please consult the Sherpa/Romeo database http://www.sherpa.ac.uk/romeo/ ; some publishers authorize deposit on open access of the postprints, sometimes with an embargo period, others authorize the deposit of the publisher-generated pdf.