UPDATE:
Exporting a project (or pages within a project) is still available in ProtoShare 5 (released Feb. 28, 2011), but the steps to get there are as follows:
1. Click the Pages tab.
The export functionality is available via the File menu in the Pages tab.
2. Select the pages to include (optional).
The export includes content from the selected pages only. Linked pages not explicitly specified are not included in the archive.
3. Open the Export Pages dialog.
Select the appropriate export choice from the File menu.
4. Specify a file name (optional).
5. Select the HTML Archive check box.
6. Select the designs to export.
By default, the active design is exported for each page. You can choose to export a named design instead. Also, you can optionally select the Publish to Web checkbox.
7. Click the Export button.
The Export History dialog opens and includes the exported archive. Using the toolbar controls, you can download, publish to web (or unpublish), and delete the file.