[brlcad]

It would absolutely change. GPL defines any incorporation or usage of a GPL work as a derivative work, thus effectively only permitting other GPL codes to use this library. That means any software in the Apache, Eclipse, or BSD-style ecosystems (among many others) cannot use this.

As for multiple authors, in theory you were required to have their permission to release it under the GPL (or any other open source license) in the first place. Given your uncertainty, it's possible that permission wasn't obtained and you could already be on unstable legal ground. I would reach out to all contributors and ask them for permission to release under a more flexible license like BSD/MIT or Apache2 to encourage more widespread use.