The best replacement for gpl is lgpl.

The best alternatives to gpl are rated as following:
★★★★★  lgpl
★★★★  bsd
★★★  mit
★★  apache
★★  bsd license
★★  gnu
★  mpl
★  mit license
★  gplv2
★  public domain
★  agpl
★  gpl v2
  apache license
  epl
  open source
  metano
  eula
  benzina
  creative commons

Your alternative for gpl is not listed? Suggest!
Speaking about gpl, one probably shouldn't forget about bsd.

Other search terms related to gpl and their ratings are:
★★★★★ bsd
You have in mind a companion for gpl and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of gpl in all years. Click on graph for more.
gpl
lgpl
bsd