Muchas Gracias wrote that publishers, including prominent computer science and technology professional societies ACM and IEEE, would not accept articles by Cuban authors for fear of Treasury Department fines. I checked with Deborah Cotton, who handles rights and permissions at ACM, and it turned out that that was their current policy.
But, unbeknownst to ACM, the ban has been lifted. A lawsuit challenging the ban was filed in 2004 and settled in 2007. It turns out that scientific and technical publication is now permitted. (More detail, including copies of correspondence with IEEE, is available here).
Well, it took a Federal law suit, but Cuban computer scientists and engineers and others can now be published in the US without the publisher obtaining a license.
Ms. Cotton told me that the information on the law change was forwarded to the ACM Director of Publications and/or the Publication Review Board for a formal resolution. Bernard Rous, ACM's Director of Publications, followed up with a search of the ACM Digital Library, which turned up 13 articles with authors from Cuba. He pointed out that most seemed to be co-authored with authors in Brazil or Spain, which is also consistent with Muchas Gracias' claim.
I also checked with Fran Tardo, External Communications Manager at IEEE, about their policy. She told me IEEE had requested and been granted a general license for publishing in December 2004. Based on this ruling, IEEE developed its policy for the handling of manuscripts from authors in embargoed countries. As I read it, it seems to be saying that an author from an embargoed nation would be treated the same as any other author.