Yes - as you mention I wrote about it in response to another point. Most of the external contributions to TerminusDB have been to the clients. The python community in particular has contributed extensively to that TDB client. The JS and python clients were always Apache 2 as we thought that people might want to embed.

The contributors to the server & core, which is more challenging from a getting started perspective (prolog server and Rust triple store), have had fewer active outside contributors. I was looking at these slides (17 - 22 here: https://www.slideshare.net/slidarko/mmadt-a-virtual-machinea...) earlier in the week and remarked on how few devs actually worked on most of the major DB and OSS projects. Tinkerpop is effectively written by 1.5 people! But that largely tallies with our experience. Small number of focused devs keeping a lot of the architecture in their heads while they write the code.

Those that did contribute, and we are eternally grateful to them, were happy to allow their code to be re-licensed. But I wrote to all individually and waited until they had time to think before taking any other steps. If we had been moving to a proprietary license, I think it would have been harder to get sign off, but that is pure speculation!