I think they are still looking for developers. There are no build instructions on their wiki page. Just this:
The TDE team will try their best to improve support for FreeBSD but progress will probably be slow. Additional developers or contributors willing to help porting the remaining features and applications are always welcome.
This is late but you can find the Trinity FreeBSD ports tree here.
At the time of writing, its full of snags so you'd be lucky to be able to install the whole thing. However, I use it and maybe soon me or someone else can come along and fix it so the entire port works flawlessly.