I'm not sure licensing was the only reason. A pitch that goes "we work like X, but better" is unconvincing. Especially when it ends with "in an incompatible way."
The closest Labs equivalent would be Protium, which is for writing programs like he mentioned with the sam/samterm split but with reattachability. Like all the most interesting application-level softwares for Plan 9, that actually do something for you, it wasn't released.