guix search rust-|recsel -P license|tr , '\n'|sed -e 's/^ *//' -e 's/ *$//' -e '/^$/d'|sort|uniq --count 
      1 AGPL 3+
      1 Artistic License 2.0
   1601 ASL 2.0
      8 Boost 1.0
     17 CC0
   2393 Expat
     13 FreeBSD
      3 GPL 2
      2 GPL 2+
     16 GPL 3
      5 GPL 3+
     43 ISC
      1 LGPL 2.0
      1 LGPL 2.1
      1 LGPL 2.1+
      6 LGPL 3
      3 LGPL 3+
     66 Modified BSD
     54 MPL 2.0
      1 NCSA/University of Illinois Open Source License
      1 non-copyleft
      3 OpenSSL
     57 Unlicense
      3 WTFPL 2
      1 X11
      4 Zero-Clause BSD
     18 Zlib