For those who like homework (and don't we all!) you should spend a few years reading through http://www.copyright.gov/. Its a tangled, tangled web of legality... and very very interesting. You can also look up all copyrights that are on record currently with the gov.

And as a point of curiosity, if anyone wishes to petition for the distribution of the glorious SW Holiday Special... Lucas and LFL apparently DO NOT hold the copyright for it:

Quote
1. Registration Number: PA-22-826
Title: The Star wars holiday special / a aSmith-Hemion production ; in association with aTwentieth Century-Fox Television ; director, Steve Binder ; producers, Ken Welch, Joe Layton & Mitzie Welch.
Imprint: [s.l. : s.n.], c1978.
Description: 2 videocassettes (120 min.) : sd., col. ; 3/4 in.
Note: Based on the motion picture Star wars. Deposit includes synopsis (1 p.)CRED: Written by Rod Warren, Bruce Vilanch, Pat Proft, Leonard Ripps & Mitzie Welch; music composed & conducted by Ian Fraser.
Claimant: Twentieth Century-Fox Film Corporation
Created: 1978
Published: 13Nov78
Registered: 20Nov78
Author on © Application: acTwentieth Century-Fox Film Corporation, employer for hire.
Previous Related Version: Motion picture "Star wars" prev. reg. LP47760.
Special Codes: 4/X/L

2. Registration Number: PAu-92-666
Title: The Star wars holiday special : as broadcast 11-17-78 / written by Rod Warren, Bruce Vilanch, Pat Proft, Leonard Ripps, and Mitzie Welch.
Description: 164 p.
Note: Teleplay based on the motion picture Star wars.
Claimant: acTwentieth Century-Fox Film Corporation
Created: 1978
Registered: 13Dec78
Author on © Application: Twentieth Century-Fox Film Corporation, employer for hire.
Claim Limit: NEW MATTER: teleplay.
Special Codes: 3/D

Looks like Fox owns it lock, stock and barrel... now that they have no more SW films to distribute for Lucas, perhaps they'll be persuaded to release it!