I've not heard of it, but I have heard of logotherapy, which was pioneered by V Frankl after World War Two, and has its basis in discovering personal meaning; it's closely linked to existential therapy.
Having had a brief look at the website, logosynthesis seems to be different and seems to have its basis in presuppositions about fragmentation and configurations of self. I have to confess to being very cynical about any therapy which has its basis in presuppositions at all, because I feel that in presupposing anything about a client, the therapist misses an opportunity to hear the client. Honestly, reading it doesn't convince me, I would like to hear what the basis is for the ideas that underpin it. But by all means go along to the lecture and make up your own mind. It never hurts to go and hear what ideas are out there, whether or not you agree with them.