Toucan Help says:
When getting the source for Toucan there are two main options, getting the very latest Toucan code or code from a specific release. As Toucan uses Mercurial to manage its source code you will need a copy. Then you can simply clone a copy of the repository which is available here:
Well I've looked there and I can't see it. I also checked out the support page and did a quick forum search. I did not see any mention about getting a copy of the source.