The best replacement for skeinforge is slic3r.

The best alternatives to skeinforge are rated as following:
★★★★★  slic3r
★★★★★  cura
★★★  kisslicer
★★  makerware
★★  netfabb
★  makerbot slicer

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

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



Google Trends

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skeinforge
slic3r
cura