The icons are taken from libreoffice-4.0.3.1.tar.xz (http://downloadarchive.documentfoundation.org/libreoffice/old/4.0.3.1/src/)
The set is from the human theme (icon-themes/human/cmd/). The copyright notice can be found below.

--

Copyright 2006-2007 by Gabriel Hurley. Available under the terms of the LGPL
/cmd/sc_incrementsublevels.png
/cmd/sc_decrementsublevels.png

Copyright 2009 by Daniel Foré <Daniel.p.Fore@gmail.com>, Jonian Guveli <jonian.guveli@gmail.com>, and K.Vishnoo Charan Reddy<vish@ubuntu.com>. Available under the terms of the GPL (Source: humanity-icon-theme)
/cmd/sc_printpreview.png
/cmd/lc_undo.png
/cmd/lc_redo.png
/cmd/sc_undo.png
/cmd/sc_redo.png
/cmd/lc_print.png
/cmd/sc_print.png
/cmd/lc_printdefault.png
/cmd/sc_printdefault.png
/cmd/lc_open.png
/cmd/sc_open.png
/cmd/lc_save.png
/cmd/sc_save.png
/cmd/lc_savebasicas.png
/cmd/lc_saveas.png
/cmd/lc_helpindex.png
/cmd/sc_helpindex.png
/cmd/sc_saveas.png
/cmd/sc_savebasicas.png
/cmd/lc_copy.png
/cmd/sc_copy.png
/cmd/lc_paste.png
/cmd/sc_paste.png
/cmd/lc_paste.png
/cmd/sc_paste.png
/cmd/lc_browsebackward.png
/cmd/sc_browsebackward.png
/cmd/lc_browseforward.png
/cmd/sc_browseforward.png
/cmd/lc_decrementlevel.png
/cmd/lc_helpbookmark.png
/cmd/lc_incrementlevel.png
/cmd/sc_decrementlevel.png
/cmd/sc_incrementlevel.png
/cmd/lc_moveup.png
/cmd/lc_movedown.png
/cmd/lc_outlineleft.png
/cmd/sc_outlineleft.png
/cmd/lc_outlineright.png
/cmd/sc_outlineright.png
/cmd/lc_outlineup.png
/cmd/sc_outlineup.png
/cmd/lc_outlinedown.png
/cmd/sc_outlinedown.png
/cmd/lc_firstrecord
/res/fileopen.png
/res/foldercl.png
/res/folderop.png
/res/fp015.png
/res/lc05501.png
/res/lx03141.png
/res/lc06303.png
/res/lx03189.png
/res/newdoc.png
/res/sc05501.png
/res/sc05505.png
/res/sx03141.png
/res/sx03189.png
/res/lc05505.png
/res/lc05700.png
/res/lc05501.png
/res/sc05700.png
/res/sc05701.png
/res/lc06300.png
/res/lc06301.png
/res/sc05502.png
/res/sc06300.png
/res/sc06301.png
/res/sc06331.png
/sfx2/res/favourite.png
/sfx2/res/favourite_big.png

Copyright 2009 by Daniel Foré <Daniel.p.Fore@gmail.com>, Jonian Guveli <jonian.guveli@gmail.com>, and K.Vishnoo Charan Reddy<vish@ubuntu.com>. , Modifications Copyright 2009 by Gabriel Hurley. Available under the terms of the GPL (Source: humanity-icon-theme)
/cmd/lc_recsearch.png
/cmd/sc_recsearch.png
cmd/lc_decrementsublevels.png
cmd/lc_incrementsublevels.png
cmd/lc_movedownsubitems.png
cmd/lc_moveupsubitems.png
cmd/lc_newrecord.png
cmd/lc_deleterecord.png


Copyright 2005-2006 by Jakub Steiner and Novell Inc., Copyright 2009 by Daniel Foré <Daniel.p.Fore@gmail.com>, Jonian Guveli <jonian.guveli@gmail.com>, and K.Vishnoo Charan Reddy<vish@ubuntu.com>, Combined by Gabriel Hurley 2006. Available under the terms of the GPL (combination of humanity-icon-
theme and OpenOffice Tango Icons)
/cmd/lc_crop.png
/cmd/sc_crop.png
/cmd/lc_firstpage.png
/cmd/lc_firstrecord.png
/cmd/lc_printersetup.png
/cmd/lc_previewprintoptions.png
/cmd/lc_printpagepreview.png
/cmd/sc_printersetup.png
/cmd/sc_previewprintoptions.png
/cmd/sc_printpagepreview.png
/cmd/lc_recundo.png
/cmd/sc_recundo.png
/cmd/lc_helpsearch.png
/cmd/sc_helpsearch.png
/cmd/lc_lastpage.png
/cmd/lc_lastrecord.png
/cmd/lc_nextrecord.png
/cmd/lc_prevrecord.png
cmd/lc_printpreview.png
/cmd/lc_compilebasic.png
/cmd/sc_changebezier.png
/cmd/lc_changebezier.png
/cmd/lc_changepolygon.png
/cmd/lc_gotoendofdoc.png
/cmd/lc_gotostartofdoc.png
/cmd/lc_firstpage
/cmd/lc_filecontrol.png
/cmd/lc_dbformopen.png
/res/lc10630.png
/res/sc10630.png
/res/sc10724.png
/res/browse.png


Copyright 2002-2004 by Novell Inc., Copyright 2009 by Daniel Foré <Daniel.p.Fore@gmail.com>, Jonian Guveli <jonian.guveli@gmail.com>, and K.Vishnoo Charan Reddy<vish@ubuntu.com>, Combined by Gabriel Hurley 2006. Available under the terms of the GPL (combination of humanity-icon-theme and OpenOffice Industrial Icons)
/cmd/lc_runbasic.png
/cmd/sc_insertctrl.png
/cmd/lc_insertctrl.png
/cmd/lc_insertfieldctrl.png
/cmd/sc_insertfieldctrl.png
/cmd/lc_dbqueryopen.png
/cmd/lc_dbreportopen.png
/cmd/lc_dbtableopen.png
/cmd/lc_loadbasic.png
