You can access the demo on MODDB download page here or on the mod website mainpage here.
IMPORTANT NOTICE:
-demo do NOT follow original Blitzkrieg requirements
-clean Blitzkrieg 1 installation is not required but is advisable
-textures settings MUST be set on high
Also, read careful the install license provided. If you do not agree with it do not install.
Aleksej fon Grozni, BK Portal and MODDB will take NO responsibility for any crash or errors that might occur.