It's known Tolkien signed a contract in 1969, selling the movie rights and TV option rights of LR and H. When reading the contract, I notice a clause that I don't quite understand:

14 The Seller reserves the right to authorize and license others to write and publish sequels (as that term is hereinafter defined) subject to the terms and conditions contained in this Paragraph 14. The term "sequel” shall be construed to mean a play, novel, short story, novella, or other literary work, written or published subsequent to the date of this agreement, containing any character or characters who have been portrayed in the Work, and in which sequel they are portrayed or participate in similar or different incidents situations, settings and events to or from those in the Work. Seller agrees that it will not sell, license or otherwise dispose of any of the right to such sequel as have been granted to the Purchaser hereunder with respect to the Work, unless Seller shall have given to the Purchaser the option, on forty-five (45) days prior written notice, to acquire such rights upon the terms and conditions (which shall be set forth at length in such notice) of any bona fide offer received by the Seller for such rights. Should the Purchaser fail or neglect to exercise such option within such forty-five (45) day period, then the Seller may sell, license or otherwise dispose of such rights to any other party within eighteen (18) months from the giving of notice to the Purchaser as aforesaid, upon the terms and conditions of such bona fide offer;

In the event that Seller does not consummate the sale, license or other disposition of such rights within such eighteen (18) months period, then Seller shall not thereafter sell, license or otherwise dispose of such rights without giving the Purchaser a new forty-five (45) day option upon such notice and upon the same terms and conditions as set forth in this paragraph 14.

Should Purchaser not acquire such rights to such sequel, then Seller covenants and agrees that any agreement with any third party purchaser of such rights shall prohibit the exercise of any of such rights (including without limitation the release of any feature length motion picture, the production of any play, or the exercise of any radio or television rights) for a period of no less than eighteen (18) months following the first general release of the first feature length motion picture based on the Work, in each territory of the world or the expiration of Purchaser's rights hereunder, whichever shall first occur; and in no event shall the Seller make any grant of any television rights whatsoever (live television or television series or otherwise) in said sequel except the right to televise the feature length motion picture photoplay based upon such sequel and except the right to advertise such motion picture by live, motion picture and other forms of television, limited to the extent of Purchaser’s limitation as contained in Paragraph 2 hereof.

Should Seller authorize or license any other person to write or publish sequels as in this Paragraph 14 provided, then as a condition of such authorization or license, the Seller shall require an agreement in writing by the grantee or licensee to be bound by all Of the terms, covenants and provisions of this Paragraph 14 with the same force and effect as if such grantee or licensee were the Seller named herein, such agreement specifically to recite that it is intended, among other things, for the benefit of the Purchaser and may be enforced by the Purchaser, and the Seller as a condition for the exercise of its rights hereunder agrees that forthwith after the execution of such grant or license, Seller will deliver to the Purchaser an executed counterpart of such agreement by such grantee or licensee.

Does it mean the TV right of The Silmarillion / Unfinished Tales as "sequels", can never be sold to a third party? If so, that would explain why Amazon didn't get them.