Hello,
This is provided in accordance with Section 19 of JUNOS EULA
( https://www.juniper.net/documentation/en_US/release-independent/licenses/agreements/eula-generic-en.html )
19. Third Party Software. Any licensor of Juniper whose software is embedded in the Software shall be a third party beneficiary with respect to this Agreement, and that licensor shall have the right to enforce this Agreement in its own name as if it were Juniper. In addition, certain third party software may be provided with the Software and is subject to the accompanying license(s), if any, of its respective owner(s). To the extent portions of the Software are distributed under and subject to open source licenses obligating Juniper to make the source code for those portions publicly available (such as the GNU General Public License (“GPL”) or the GNU Lesser General Public License (“LGPL”)), Juniper will make those source code portions (including Juniper modifications, as appropriate) available upon request for a period of up to three years from the date of distribution. You may obtain a copy of the GPL at http://www.gnu.org/licenses/gpl.html, and a copy of the LGPL at http://www.gnu.org/licenses/lgpl.html. Open source information and information on contacting Juniper can be found at http://www.juniper.net/support/.
You can certainly use these source code files for the purposes outlined in GPL/LGPL.
To my knowledge, no publicly available documentation exists on how to actually make use of these source code files, so You are on Your own in this regard.
HTH
Thx
Alex