Hi-
Thank you for your interest in Qdabra's products.
DBXL will install on WSS 3.0. As with all DBXL installations, need to make sure you install on the SharePoint port 80 site.
DBXL will add the Network Service account (or whatever account the DBXL App pool will be using) to WSS_WPG (when DBXL is installed on a SharePoint site) or IIS_WPG (when DBXL is installed on a non-SharePoint site). The DBXL installer also grants db_datareader and db_datawriter permissions to the application pool. An administrator should do the install, but regular users can call the web service if they are granted permissions.
For more info check out the DBXL Installation Guide and the Getting Started guide.
Thank you.