Ancestry requires a subscription to access all but the 1921 census (which is free to view with free registration), access to LAC is completely free (no registration or subscription).
Microfilm of Canadian census records can be viewed at any Family History Centre worldwide. For those within Canada it can also be viewed at LAC and any Canadian library or archive with microfilm capabilities.
For terms of use of LAC images see: Using Files Located on Non-Government of Canada Servers and Copyright / Permission to Reproduce
1 Library and Archives Canada Agreement with Ancestry.ca, Library and Archives Canada Partners with Ancestry.ca