I suggest looking at these for background info:
And from what I know, the grab cursor included as part of Webkit is freely useable as is - if I'm incorrect, or it's not to your taste, it's the work of a few minutes to create your open open-hand / grab cursor in Illustrator, Inkscape, Sketch app or Affinity Designer, and export as a
.png, then use an online converter to make that into a
Failing that, the Entypo+ glyph set is free to use, comes as sheer vector, and has a nice vector open hand glyph in it - easy to convert.
Also consider looking at the resources of The Noun Project which are all royalty-free, open source, and pretty darn well developed.
Hope this helps.