The best replacement for buddypress is bbpress.

The best alternatives to buddypress are rated as following:
★★★★★  bbpress
★★★★  elgg
★★★★  ning
★★★★  jomsocial
★★★  mingle
★★  symposium
★★  socialengine
★★  multisite
★★  vbulletin
★  oxwall
★  phpfox
★  social engine
★  phpbb
★  wp symposium
  pligg
  userpro

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

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



Google Trends

Scale is based on the average worldwide traffic of buddypress in all years. Click on graph for more.
buddypress
bbpress
elgg