In brief, one can obtain a bibtex entry (from crossref) from a DOI in a single request. On the command-line, it looks like
curl -LH "Accept: application/x-bibtex" https://doi.org/10.1126/science.169.3946.635.
Using this, it should not be too hard to create a feature in Jabref to add a new entry from a DOI. I would consider such a feature extremely useful. What is your opinion about it?