Documentation/4.1/FAQ

Is slicer really free?

Yes, really, truly, free. Not just a free trial. No pro version with all the good stuff. Slicer is free with no strings attached. You can even re-use the code in any way you want with no royalties and you don't even need to ask us for permission. (Of course we're always happy to hear from people who've found slicer interesting).

See the Slicer License page for the legal version of this.

Can I use slicer for patient care?

Slicer is intended for research work and has no FDA clearances or approvals of any kind. It is the responsibility of the user to comply with all laws and regulations (and moral/ethical guidelines) when using slicer.