In order to make clear which versions of SugarCRM a particular module is suitable for, I will use the following guideline for installable modules, themes, etc from now on:

moduleName-compatibleVersions-moduleVersion

And the module package:

moduleName-compatibleVersions-moduleVersion.zip

Such as:

• config-5.x-0.5.zip
  To indicate the module is compatible with all SugarCRM versions in the 5.x branch up to the day that the module was released. So releasing it in December 2009 (current version: 5.5) doesn't mean it's compatible with 5.6 (hypothetically released in March 2010).
• xyz-5.0-5.2-0.3.zip
  To indicate the module is compatible with SugarCRM 5.0.xx, 5.1.xx and 5.2.x, but not 5.5.0