Before compiling:

Check the various defines in udapp.pp and demos.inc:

EXPORTPDF - enable export to PDF
EXPORTFPIMAGE - enable export to image
EXPORTHTML - enable export to html

To enable the following defines, check the lcldemo and fpguidemo projects in Lazarus/FPGUI:
EXPORTLCL - enable export to LCL (preview)
EXPORTAGGPAS - enable export to aggpas
EXPORTFPGUI - enable export to fpgui (preview)

Bare-bones use (only fcl needed):

- compile fcldemo.pp
- compile webdemo.pp

run without cmd-line params to see usage.