An interesting tool has been included in the latest version of gvSIG Online that allows unregistered users to add an external vector layer or a web service into a project.
In both cases, a group of layers is created at the end of the Table of Contents, below the rest of the groups, and it only remains active during that session, so it disappears when the web page is refreshed. One of the advantages is that if the user prints a geoportal with an imported layer, it is shown in the PDF file.
The vector layer import tool allows to load SHP, KML and JSON files. In the case of SHP files, the 3 mandatory files (SHP, SHX and DBF) must be compressed into a .ZIP file. In the current version, the reference system of these files must be EPSG 4326 (WGS84), although the objective in the future is that they can be imported in another reference system.
Regarding the web services import tool, it currently allows to load WMS and WFS service layers.
Here you have a video about how this tools work:
More information about gvSIG Online implementation: firstname.lastname@example.org