Use of Vagrant in tests poses licencing question

[Sam James]

Hi,

I noticed that a recent commit
(07c87e1af3f3ddf2ff12cf90baae2a897d13ea25,
testsuite: Make it easier to run test on other machines.)
uses Vagrant for testing GNU Parallel on remote machines.

Vagrant, however, is not free software. It was previously licenced
under the MIT licence, but is now licenced under the BUSL ('Business
Source Lience') licence, which does not appear to be free.

Should GNU Parallel continue to rely on non-free software?

[0] 
https://git.savannah.gnu.org/cgit/parallel.git/commit/?id=07c87e1af3f3ddf2ff12cf90baae2a897d13ea25

thanks,
sam