what's the difference between regular zotero and juris-m?

Regular zotero is a general purpose scholarly open-source citation and research manager. It is optimized for broad appeal and usefulness in all areas of scholarly research. It works on Windows, Mac, and Linux operating systems, has plugins for Microsoft Word, LibreOffice, and OpenOffice word processors, and works with Google Docs, email, and many other applications. You have a choice of using it with Firefox, Chrome, or Safari. You may store data in any language, and the zotero interface and documentation are available in most languages (see the zotero language support pages for more information). Regular zotero will not, however, allow you to store transliteration/translation information as a part of the citation, which can be important when using sources that are not in roman alphabet languages. Its support of American legal citation (the Bluebook) is rudimentary, but adequate for most things. You will need to supply the Bluebook abbreviation for any journal title you cite every time you add one to your zotero library. It has automatic journal abbreviations, but legal scholars should not use this right now, as they default to Medline abbreviations, which differ greatly from the Bluebook. All citations will have to be checked to make sure they follow the Bluebook rules (they do a pretty good job in most cases, but need a little tweaking here and there). Finally, not all legal material types are specifically supported (e.g., treaties) and you will need to adapt other material types by hand. This is not hard to do.

Juris-M, a multi-lingual branch of zotero for legal scholars, is an offshoot of regular zotero created by Professor Frank G. Bennett of the Graduate School of Law at Nagoya University in Japan. An early adopter of zotero, Prof. Bennett needed it to advance faster than zotero's primary creators were able to allow (they had to be concerned with stability and broad appeal). So he forked the code into an experimental version he calls juris-m. This version handles law-related materials much better than regular zotero, and it also allows transliteration/translation metadata storage as well. Juris-m has both standalone and Firefox versions, and works with all the browsers regular zotero works with. It works in Windows, Mac, and Linux operating systems, and uses the zotero.org accounts and sync tools. One caveat, you can't mix regular zotero and juris-m versions in the same account. The changes that allow juris-m to handle language support and legal citation make the databases incompatible. The current plan is for regular zotero to incorporate all the changes juris-m has made within the next few years.

Juris-m also comes with a couple of plugins that make legal citation better. They are available at Juris-m's website.. The first of these is the abbreviation filter and lists of legal abbreviations. This makes automatic Bluebook abbreviations. The second is the Free Law Ferret, which has perhaps the best name ever given a research tool. The Free Law Ferret adds an item to the Firefox context menu (the one you usually right-click to open) that if chosen will scrape the web page you are looking at for any citations to US case law. It will then retrieve these cases from free law sources (such as Google Scholar or CourtListener) for you and store them in your juris-m database.