We've got incomplete versions of the tokipona.org site in the Wayback machine since Feb 2002
We've got the 2009 wiki version, which I think is a public work in progress as of Dec 2009.Canon by Community Repute: Wikipedia, As much of an authority as it is for anything on Wikipedia
We've got 100s of versions of the wikipedia article since April 2002
and todays version. Today's version can change at any moment and the result will depend on the people who care enough to edit.Canon by Community Repute: First among equal fan sitesJan Pije's lessons
.Canon by Data: Attested usages
Attested usage is the various attempts to use the language. If no one has used a particular phrase (or uses it rarely), then it might be wrong. If it has been used over a long period of time, then it might be right. Its the difference between de jure and de facto law.Canon by Data: Opinion of "fluent" speakers
Its probably an uncontroversial fact that there are fluent Russian and English speakers, who they are and that if asked these speakers can say if a sentence is valid Russian or English. We probably could argue over who is fluent, or if their opinion counts. It might be a while before we can check grammaticality and get consensus from such a survey.
Am I missing any sources of canon, or failing that, techniques for answering, "What is toki pona and what is not toki pona?"